Nanocrystal doped matrixes

ABSTRACT

Matrixes doped with semiconductor nanocrystals are provided. In certain embodiments, the semiconductor nanocrystals have a size and composition such that they absorb or emit light at particular wavelengths. The nanocrystals can comprise ligands that allow for mixing with various matrix materials, including polymers, such that a minimal portion of light is scattered by the matrixes. The matrixes of the present invention can also be utilized in refractive index matching applications. In other embodiments, semiconductor nanocrystals are embedded within matrixes to form a nanocrystal density gradient, thereby creating an effective refractive index gradient. The matrixes of the present invention can also be used as filters and antireflective coatings on optical devices and as down-converting layers. Processes for producing matrixes comprising semiconductor nanocrystals are also provided. Nanostructures having high quantum efficiency, small size, and/or a narrow size distribution are also described, as are methods of producing indium phosphide nanostructures and core-shell nanostructures with Group II-VI shells.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/034,216, filed Jan. 13, 2005, entitled “Nanocrystal DopedMatrixes” by Parce et al., which issued on May 20, 2008, as U.S. Pat.No. 7,374,807, and which claims priority to and benefit of provisionalU.S. Patent Application No. 60/536,962, filed Jan. 15, 2004, and U.S.Provisional Patent Application No. 60/635,784, filed Dec. 15, 2004, thefull disclosures of which are hereby incorporated by reference in theirentirety for all purposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Portions of this invention may have been made with United StatesGovernment support under Department of Energy grant DE-FG02-04ER84020entitled “High Efficiency Nanocomposite White Light Phosphors.” As such,the United States Government may have certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to nanocomposite matrixes, includingpolymeric layers comprising nanocrystals, and processes for preparingnanocrystal doped matrixes. The invention also relates to nanostructureligands, including miscibility-enhancing ligands. The invention alsorelates to nanostructures having high quantum efficiency, small size,and/or a narrow size distribution, as well as to methods of producingindium phosphide nanostructures and core-shell nanostructures with GroupII-VI shells.

BACKGROUND OF THE INVENTION

High performance down-converting phosphor technologies will play aprominent role in the next generation of visible light emission,including high efficiency solid-state white lighting (SSWL). Inaddition, such technologies are also applicable to near infrared (NIR)and infrared (IR) light emitting technologies. Down-conversion fromultraviolet (UV) or blue light emitting semiconductor light emittingdiodes (LEDs) into blue, red and green wavelengths offers a fast,efficient and cost-effective path for delivering commercially attractivewhite light sources. Unfortunately, existing rare-earth activatedphosphors or halophosphates, which are currently the primary source forsolid-state down-conversion, were originally developed for use influorescent lamps and cathode ray tubes (CRTs), and therefore have anumber of critical shortfalls when it comes to the unique requirementsof SSWL. As such, while some SSWL systems are available, poor powerefficiency (<20 light lumens/watt (lm/W)), poor color rendering (ColorRendering Index (CRI)<75) and extremely high costs (>$200/kilolumen(klm)) limit this technology to niche markets such as flashlights andwalkway lighting.

Furthermore, LEDs often suffer from reduced performance as a result ofinternal reflection of photons at the chip/coating interface. Typically,LEDs are encapsulated or coated in a polymeric material (which maycomprise phosphors) to provide stability to the light-emitting chip.Currently these coatings are made by using an inorganic or organiccoating that has a very different refractive index than the basematerial (i.e., the chip), which results in a detrimental optical effectdue to the refractive index mismatch at the interface between the twomaterials. In addition, the temperature of the LED can reach in excessof 100° C. To allow for the expansion and contraction that can accompanythis temperature rise, a compliant polymeric layer (e.g., silicone) isoften placed in contact with the chip. In order to provide additionalstability to the LED, this compliant layer is often further coated witha hard shell polymer.

The resulting LED structure suffers loss of light at the chip/compliantpolymer interface due to the lower refractive index of the polymercoating in relation to the LED. However, if the refractive index of thecompliant layer is increased, even greater loss will occur due at thehigh refractive index/low refractive index interface between thecompliant polymer and the hard shell polymer due to internal reflection.

There are several critical factors which result in poor powerefficiencies when using traditional inorganic phosphors for SSWL. Theseinclude: total internal reflection at the LED-chip and phosphor layerinterface resulting in poor light extraction from the LED into thephosphor layer; poor extraction efficiency from the phosphor layer intothe surroundings due to scattering of the light generated by thephosphor particles as well as parasitic absorption by the LED chip,metal contacts and housing; broad phosphor emission in the redwavelength range resulting in unused photons emitted into the near-IR;and poor down-conversion efficiency of the phosphors themselves whenexcited in the blue wavelength range (this is a combination ofabsorption and emission efficiency). While efficiencies improve with UVexcitation, additional loss due to larger Stokes-shifted emission andlower efficiencies of LEDs in the UV versus the blue wavelength rangemakes this a less appealing solution overall.

As a result, poor efficiency drives a high effective ownership cost. Thecost is also significantly impacted from the laborious manufacturing andassembly process to construct such devices, for example theheterogeneous integration of the phosphor-layer onto the LED-chip duringpackaging (DOE and Optoelectronics Industry Development Association“Light emitting diodes (LEDs) for general illumination,” TechnologyRoadmap (2002)). Historically, blue LEDs have been used in conjunctionwith various band edge filters and phosphors to generate white light.However, many of the current filters allow photon emission from the blueend of the spectrum, thus limiting the quality of the white LED. Theperformance of the devices also suffer from poor color rendering due toa limited number of available phosphor colors and color combinationsthat can be simultaneously excited in the blue. There is a needtherefore for efficient nanocomposite filters that can be tailored tofilter out specific photon emissions in the visible (especially the blueend), ultraviolet and near infrared spectra.

While some development of organic phosphors has been made for SSWL,organic materials have several insurmountable drawbacks that make themunlikely to be a viable solution for high-efficiency SSWL. Theseinclude: rapid photodegradation leading to poor lifetime, especially inthe presence of blue and near-UV light; low absorption efficiency;optical scattering, poor refractive index matching at thechip-interface, narrow and non-overlapping absorption spectra fordifferent color phosphors making it difficult or impossible tosimultaneously excite multiple colors; and broad emission spectra. Thereexists a need therefore for polymeric layers that aid production of highquality, high intensity, white light.

The present invention fulfills these needs by providing polymericnanocomposites that function as down-converting layers, photon-filteringlayers and/or refractive index matching layers, by taking advantage ofthe ability to tailor nanocrystals to maximize their emission,absorption and refractive index properties.

SUMMARY OF THE INVENTION

The present invention provides matrix materials doped with nanocrystalsthat have specific emission and/or absorption characteristics and alsoallow for specific tailoring of refractive indexes of thenanocomposites.

In one embodiment, the present invention provides polymeric layerscomprising a polymer and semiconductor nanocrystals embedded within thepolymer, wherein the nanocrystals have a size and a composition suchthat they absorb visible, ultraviolet, near-infrared and/or infraredlight, and wherein the polymeric layers scatter a minimal portion oflight that enters the layers. In certain embodiments, the polymer issilicone. The polymeric layers of the present invention can be used tocoat optical devices (e.g., refractive lenses or reflective elements) orcan be used to encapsulate active devices, such as a light emittingdiodes (LEDs). Suitably, the polymeric layers of the present inventionthat absorb visible light will absorb red light, blue light and/or greenlight.

The nanocrystals utilized throughout the embodiments of the presentinvention will suitably be between about 1-10 nm in size, about 1-4 nmin size or about 1-3 nm in size and can further comprisemiscibility-enhancing ligands attached to their surface to aid in mixingwith the polymers. The polymeric layers of the present invention canhave any effective refractive index between that of the pure polymer andthe pure nanocrystals, and will suitably have an effective refractiveindex greater than about 1.5 and in certain embodiments about 1.8. Incertain embodiments, the polymeric layers of the present invention willbe greater than about 0.5 mm in thickness. Suitable polymers includesilicone.

In another embodiment, the present invention provides polymeric layerscomprising a polymer and semiconductor nanocrystals embedded within thepolymer, wherein the polymeric layer has an effective refractive indexgreater than the polymer alone, and wherein the polymeric layer scattersa minimal portion of light that enters the polymeric layer. Suitably,the polymeric layers will scatter less than about 50%, less than about20% or less than about 15% of light that enters the polymeric layers. Insuitable embodiments, the nanocrystals will be ZnS nanocrystals and thepolymeric layers will be greater than about 0.5 mm in thickness.

In another embodiment, the present invention provides polymeric layersthat encapsulate an active device (e.g., an LED) that has an effectiverefractive index, n₁. The layer comprises a polymer and semiconductornanocrystals embedded within the polymer. The layer has an innerboundary in contact with the active device and an outer boundary incontact with a medium having an effective refractive index, n₂, whereinthe layer has an effective refractive index less than or equal to n₁ atthe inner boundary and an effective refractive index greater than orequal to n₂ at the outer boundary. In certain embodiments, effectiverefractive index n₁ will be greater than n₂, suitably greater than about1.5, and in certain embodiments about 1.8. In certain such embodiments,the layer will have a nanocrystal density gradient, being highest at theinner boundary and lowest at the outer boundary. Suitably thisnanocrystal density gradient will be substantially linear throughout thepolymeric layer. The nanocrystals optionally have a size and acomposition such that they absorb visible (e.g., red, blue and/orgreen), ultraviolet, near-infrared and/or infrared light.

The present invention also provides processes for preparing polymericlayers, comprising mixing semiconductor nanocrystals at a first densitywith a solvent and a polymer to form a first mixture, coating asubstrate material with the first mixture and evaporating the solvent toform the polymeric layer, wherein the polymeric layer has an effectiverefractive index of n₁.

The processes of the present invention can be used to prepare polymericlayers for coating active devices (e.g., LEDs), or optical devices(e.g., refractive lenses or reflective elements). The processes of thepresent invention can utilize nanocrystals which further comprisemiscibility-enhancing ligands attached to their surface.

In suitable embodiments, the processes of the present invention canfurther comprise mixing semiconductor nanocrystals at a second densitywith a solvent and a polymer to form a second mixture, coating thesubstrate material with the second mixture and evaporating the solventto form a second polymeric layer, wherein the second polymeric layer hasan effective refractive index of n₂. In other embodiments, the processescan further comprise repeating these steps with a third through i^(th)density of semiconductor nanocrystals to produce third through i^(th)polymeric layers, wherein the third through i^(th) polymeric layers haveeffective refractive indices, n₃ through n_(i), respectively. In certainsuch embodiments, the effective refractive index n₁ will be greater thann₂ and the effective refractive index of the i^(th) polymeric layer willbe less than the effective refractive index of any other polymericlayer. The processes of the present invention can further comprisecentrifuging the first mixture of semiconductor nanocrystals, solventand polymer, to form a nanocrystal density gradient within the mixtureprior to coating the substrate material.

In suitable embodiments of the processes of the present invention, thecoating can be via spin coating or screen printing. As discussedthroughout, the nanocrystals used in the processes of the presentinvention can have a size and a composition such that they absorb lightat a particular wavelength. In other embodiments, the nanocrystals canbe tuned so as to emit light at a particular wavelength. In otherembodiments, the process of the present invention can utilizesemiconductor nanocrystals that comprise two or more different sizes orcompositions and therefore can have different properties. The polymericlayers produced by the processes of the present invention will suitablybe greater than about 0.5 mm in thickness.

In another embodiment, the present invention provides solid state whitelighting devices comprising a power efficiency greater than 25 lm/W,suitably greater than 50 lm/W, greater than 100 lm/W, greater than 150lm/W, or greater than 200 lm/W.

In other embodiments, the solid state white lighting devices comprise adown converting nanocomposite that comprises two or more semiconductornanocrystals tuned to emit light at one or more selected wavelengths.The solid state white lighting devices of the present invention willsuitably provide a CRI of greater than about 80. In still otherembodiments, the solid state white lighting devices comprise a matrixcoupled to the two or more semiconductor nanocrystals via one or morechemical moieties.

Another embodiment the present invention provides down convertingnanocomposite devices, comprising two or more semiconductor nanocrystalphosphors of two or more sizes, the nanocrystal phosphors tuned to emitlight at one or more selected wavelengths, and providing a CRI ofgreater than about 80; a matrix with a high index of refraction, low UVdegradation and/or matched thermal expansion; and a chemical structurecoupling the matrix to the nanocrystal phosphors. Suitably, the two ormore semiconductor nanocrystal phosphors will comprise a core-shellstructure, wherein a shell (e.g., ZnS) provides a type I band gap withrespect to a core. The core-shell nanocrystals of the present inventionwill suitably have a quantum efficiency of about 10% to about 90%.

In further embodiments of the present invention, the two or moresemiconductor nanocrystal phosphors are color matched and the matrix cancomprise TiO₂. In yet further embodiments, the nanocomposite can belayered on an LED substrate which comprises sapphire or SiC. Suitably,the matrix will be a compliant layer that can withstand the thermalexpansion that results when the LED heats up, and suitably will besilicone. Suitably, the matrix has a refractive index that is the sameas the LED substrate.

In another embodiment, the present invention provides polymeric layers,comprising a polymer; and semiconductor nanocrystals embedded within thepolymer, wherein the nanocrystals have miscibility-enhancing ligandsconjugated to their surface, and wherein the ligands comprise an alkanechain of between 6 and 18 carbons in length. In suitable embodiments,the ligands can comprise an alkane chain of between 12 and 18 carbons inlength. The polymer will suitably be silicone, and the semiconductornanocrystals will suitably have a size between about 1-10 nm (e.g., 1-4nm or 1-3 nm), and in certain embodiments will be ZnS nanocrystals. Incertain embodiments, the polymeric layers will scatter a minimal portionof light that enters said polymeric layer (e.g., less than about 50%,less than about 20%, or less than about 15% of light that enters saidpolymeric layer). Suitably, the layer will be greater than about 0.5 mmin thickness.

In one aspect, the invention provides nanostructures having ligands ofthe invention bound to their surface. As described throughout, thenanostructures are optionally nanocrystals or quantum dots, e.g.,inorganic, semiconductor, or metal nanocrystals. In certain embodiments,the nanostructures are core-shell nanostructures. A number of exemplaryligands are described.

One general class of embodiments provides a composition comprising ananostructure and a ligand bound to a surface of the nanostructure,which ligand comprises a body group comprising an organic moiety, a headgroup coupled to the body group, and a tail group coupled to the bodygroup. The head group comprises a nanostructure binding moiety, and thetail group comprises a silicone moiety.

The body group optionally comprises an unsaturated moiety, for example,an aryl moiety, an alkene moiety, an alkyne moiety, or the like. Inother embodiments, the body group comprises an alkyl moiety. Forexample, the body group can be an alkane chain moiety that contains oneor more carbons, e.g., 1-20 carbons. In one embodiment, the body groupis a linear alkyl moiety three carbons or four carbons in length.

The nanostructure binding moiety can be essentially any moiety thatbinds or is capable of binding to the surface of the nanostructure.Examples include, but are not limited to, a carboxylic acid moiety, amonocarboxylic acid moiety, a dicarboxylic acid moiety, a phosphonatemoiety, a diethylphosphonate moiety, a bistrimethylsilylphosphonatemoiety, a thiol moiety, or an amine moiety.

In one class of embodiments, the tail group comprises a linear siliconemoiety. In other embodiments, the tail group comprises a cyclic siliconemoiety, a branched silicone moiety, or a silsesquioxane moiety.

One general class of embodiments provides a composition comprising ananostructure and a polymeric ligand bound to a surface of thenanostructure. The polymeric ligand comprises a linear silicone backboneand one or more nanostructure binding moieties coupled to the siliconebackbone.

The polymeric ligand includes two or more monomer units. As just a fewexamples, a monomer unit can be a dimethylsiloxane group, aphenylmethylsiloxane group, or a siloxane group bearing a nanostructurebinding moiety. The monomer units within the ligand can be of the sametype or of different types. In ligands including two or more differenttypes of monomer units, the ligand can, e.g., include a block copolymeror a random copolymer of the units.

As for the embodiments above, the nanostructure binding moiety can beessentially any moiety that binds or is capable of binding to thesurface of the nanostructure, e.g., a carboxylic acid moiety, amonocarboxylic acid moiety, a dicarboxylic acid moiety, a phosphonatemoiety, a diethylphosphonate moiety, a bistrimethylsilylphosphonatemoiety, a thiol moiety, or an amine moiety. The ligand optionallycomprises two or more nanostructure binding moieties, e.g., three ormore, five or more, 10 or more, or even 20 or more; each of thenanostructure binding moieties is typically coupled to a differentsilicon atom in the silicone backbone. In one class of embodiments, eachof the one or more nanostructure binding moieties is coupled to thesilicone backbone through an alkyl moiety.

One general class of embodiments provides a composition comprising ananostructure and a ligand bound to a surface of the nanostructure,which ligand comprises a body group comprising an alkyl moiety, a headgroup coupled to the body group, and a tail group coupled to the bodygroup. The head group comprises a nanostructure binding moiety, and thetail group comprises an unsaturated moiety or a silane moiety.

As for the embodiments above, the nanostructure binding moiety can beessentially any moiety that binds or is capable of binding to thesurface of the nanostructure, e.g., a carboxylic acid moiety, amonocarboxylic acid moiety, a dicarboxylic acid moiety, a phosphonatemoiety, a diethylphosphonate moiety, a bistrimethylsilylphosphonatemoiety, a thiol moiety, or an amine moiety.

In one class of embodiments, the body group is a linear alkyl moiety.The linear alkyl moiety includes one or more carbons, for example, 1-20carbons. In one embodiment, the body group is a linear alkyl moietythree carbons or four carbons in length.

In embodiments in which the tail group comprises an unsaturated moiety,the moiety can be an alkene moiety (e.g., a monoalkene, dialkene, ordiene), an alkyne moiety, an aromatic moiety, an aryl moiety, or thelike. In embodiments in which the tail group comprises a silane moiety,the silane moiety includes a silicon atom with three independentlyselected organic substituents. For example, the silicon atom can havethree alkene substituents or three aromatic or aryl substituents. In oneclass of embodiments, the tail group comprises a trialkyl silane moiety.

A composition of the invention optionally includes a plurality orpopulation of the ligand-bound nanostructures. In one aspect, thecomposition comprises a plurality of the nanostructures, each of whichhas the ligand bound to its surface, and a polymer in which thenanostructures are embedded. The polymer can be, for example, a siliconepolymer (e.g., in embodiments in which the ligand has a silicone tailgroup or substituent) or a hydrocarbon or other organic polymer (e.g.,in embodiments in which the ligand has an alkyl, alkene, or otherhydrocarbon tail or substituent).

One general class of embodiments provides a composition including ananostructure and a ligand bound to a surface of the nanostructure,where the ligand is a dicarboxylic or polycarboxylic acid other than apoly(norbornene)-poly(norbornene-dicarboxylic acid) diblock copolymer(e.g., any of the carboxylic acid ligands described herein). In oneclass of embodiments, the nanostructure comprises a semiconductor otherthan ZnO or ZnS. In another class of embodiments, the nanostructure is ametal nanostructure. In one aspect, the nanostructure is a core-shellnanostructure.

In other aspects, the invention provides nanostructures and methods ofmaking nanostructures. One general class of embodiments provides methodsfor production of InP nanostructures. In the methods, a first precursor,e.g., indium acetate, and a second precursor, e.g.,tris(trimethylsilyl)phosphine, are provided. The first and secondprecursors are reacted in the presence of an acid and a solvent toproduce the nanostructures. The solvent is preferably a solvent otherthan octadecene. For example, the solvent can be TOPO, TOP,benzophenone, hexadecane, octadecane, or another solvent with asimilarly high boiling point. In one class of embodiments, the acid is afatty acid, for example, lauric acid, capric acid, myristic acid,palmitic acid, or stearic acid. In other embodiments, the acid is aphosphonic acid, a dicarboxylic acid, or a polycarboxylic acid, forexample, one of those described herein or known in the art.

Another general class of embodiments provides methods for production ofcore-shell nanostructures having Group II-VI semiconductor shells. Inthe methods, a nanostructure core is provided, and a shell surroundingthe core is produced by providing a first precursor comprising a GroupII atom, providing a second precursor comprising a Group VI atom, andreacting the first and second precursors in the presence of a ligand toproduce the shell. The ligand is a dicarboxylic or polycarboxylic acid.Exemplary first precursors include diethylzinc, dimethyl zinc, zincoxide, zinc stearate, and zinc acetate. Exemplary second precursorsinclude hexamethyldisilthiane and elemental sulfur.

One general class of embodiments provides a composition comprising apopulation of nanostructures, which population displays a quantumefficiency of 50% or greater. A member nanostructure of the populationcomprises a core and a shell, which core is other than a Cd-containingcore or a Pb-containing core. Optionally, the population displays aquantum efficiency of 55% or greater, e.g., about 60% or more.

In one class of embodiments, a ligand is bound to a surface of themember nanostructure. Exemplary ligands include, but are not limited to,those described herein, for example, dicarboxylic acid ligands. In oneclass of embodiments, the core comprises a Group III-V semiconductor,e.g., InP. In one class of embodiments, the shell comprises a GroupII-VI semiconductor such as ZnS, ZnSe, or ZnSe_(x)S_(1-x). In one classof embodiments, the member nanostructure comprises an InP core,optionally, with a ZnS, ZnSe, or ZnSe_(x)S_(1-x) shell, and optionallywith a ligand bound to a surface of the nanostructure.

One class of embodiments provides a composition comprising a populationof InP nanocrystals, wherein the average diameter of the nanocrystals inthe population is less than 2.5 nm, e.g., less than 2.0 nm.

One class of embodiments provides a composition comprising a populationof InP nanocrystals, wherein a luminescence spectrum of the populationhas a full width at half maximum of less than 70 nm. For example, thefull width at half maximum can be less than 60 nm, less than 50 nm, oreven 40 nm or less. The nanocrystals are optionally small, e.g., 1-6 nmor 1.5-5.5 nm in size; optionally, the emission spectrum of thepopulation has an emission maximum between 500 nm and 750 mm.

In one aspect, the present invention provides luminescent nanocompositesand methods for incorporating luminescent nanostructures into curablematrices while preserving the luminescent properties into the solidstate. The nanostructures optionally have ligands bound to theirsurface, including novel ligands of the invention and/or other tightlybinding ligands.

One general class of embodiments thus provides a luminescentnanocomposite comprising a population of luminescent nanocrystals, whichnanocrystals are embedded in a matrix, and which nanocrystalssubstantially retain their luminescence when embedded in the matrix. Thematrix is preferably an epoxy, polyurea, or polyurethane matrix. Asnoted, the nanocrystals remain luminescent when embedded in the matrix.Thus, light output of the composite is optionally at least 5%, at least10%, at least 20%, or at least 30% or more of light output of acomparable population of nanocrystals not embedded in the matrix.

In one class of embodiments, a ligand is bound to a surface of a membernanocrystal, and the ligand includes an amine moiety or a dicarboxylicacid moiety that binds to the surface of the member nanocrystal.

In one aspect, the nanocrystals are non-Cd containing nanocrystals. Inone embodiment, the nanocrystals are core-shell nanocrystals, and thecores comprise a Group III-V semiconductor. As just a few examples, thenanocrystals can be InP/ZnS, InP/ZnSe, or InP/ZnSe_(x)S_(1-x) core-shellnanocrystals or InP/ZnSe/ZnS core/shell/shell nanocrystals.

A related general class of embodiments provides a luminescentnanocomposite comprising a population of luminescent nanocrystalsembedded in a matrix, wherein a ligand is bound to a surface of a membernanocrystal. The ligand preferably comprises an amine moiety or adicarboxylic acid moiety that binds to the surface of the membernanocrystal. Preferably, as for the embodiments above, the nanocrystalssubstantially retain their luminescence when embedded in the matrix.

Essentially all of the features noted for the embodiments above apply tothese compositions as well, as relevant; for example, with respect totype of nanocrystal, type of ligand, and/or the like. For example, thenanocrystals are optionally non-Cd containing nanocrystals. In oneembodiment, the matrix comprises epoxy, polyurea, or polyurethane.

The invention also provides methods of making such luminescentcomposites. Thus, one general class of embodiments provides methods ofproducing a luminescent nanocomposite, in which luminescent nanocrystalsare provided and mixed with one or more matrix precursors to form afirst mixture. The matrix precursors are cured to produce a matrix,e.g., an epoxy, polyurea, or polyurethane matrix, thereby providing thenanocomposite. The resulting nanocomposite comprises the luminescentnanocrystals embedded in the matrix, wherein the nanocrystalssubstantially retain their luminescence when embedded in the matrix. Themethods optionally include casting or forming the first mixture into adesired shape prior to curing the matrix precursors.

Essentially all of the features noted for the embodiments above apply tothese methods as well, as relevant; for example, with respect to lightoutput, composition of the nanocrystals, associated ligands, and/or thelike. For example, providing luminescent nanocrystals optionallycomprises providing luminescent nanocrystals having a ligand bound to asurface of the nanocrystals. The ligand can include an amine moiety or adicarboxylic acid moiety that binds to the surface of the nanocrystals.

A related general class of embodiments also provides methods ofproducing a luminescent nanocomposite. In the methods, luminescentnanocrystals having a ligand bound to a surface of the nanocrystals areprovided. The ligand preferably comprises an amine moiety or adicarboxylic acid moiety that binds to the surface of the nanocrystals.The nanocrystals are mixed with one or more matrix precursors to form afirst mixture, and the matrix precursors are cured to produce a matrix,thereby providing the nanocomposite comprising the luminescentnanocrystals embedded in the matrix. Preferably, the nanocrystalssubstantially retain their luminescence when embedded in the matrix. Themethods optionally include casting or forming the first mixture into adesired shape prior to curing the matrix precursors.

Essentially all of the features noted for the embodiments above apply tothese methods as well, as relevant; for example, with respect tocomposition of the nanocrystals, light output, exemplary ligands, typeof matrix, and/or the like.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure and particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the pertinent art to makeand use the invention.

FIG. 1 shows absorption and emission spectra for various nanocrystalradii showing continuous tailoring of the emission and absorptionwavelengths.

FIG. 2 shows a comparison of traditional thick phosphors integratedduring packaging, and a nanocomposite down-converting layer integratedprior to dicing, according to one embodiment of the present invention.

FIG. 3 shows the elimination of wasted light at the edges of the visiblespectrum by using phosphor nanocrystals, compared to traditionalphosphor edge losses.

FIG. 4 shows the normalized intensity generated by mixing a continuum ofnanocrystal sizes, creating broad-band white light.

FIG. 5 shows a three color emitting LED in accordance with oneembodiment of the present invention.

FIG. 6 is a cross-sectional view of a polymeric layer in accordance withone embodiment of the present invention.

FIG. 7 is a cross-sectional view of a polymeric layer having ananocrystal density gradient in accordance with one embodiment of thepresent invention.

FIG. 8 is a cross-sectional view of an optical device with a polymericlayer coating the device in accordance with one embodiment of thepresent invention.

FIG. 9 is a plot showing the effective refractive index of variousmatrixes versus volume loading ratio of ZnS nanocrystals.

FIG. 10 is a plot showing the effective refractive index of a siliconenanocomposite comprising ZnS nanocrystals as a function of wavelength.

FIG. 11 is a cross-sectional view of a light emitting diode encapsulatedwithin a polymeric layer in accordance with one embodiment of thepresent invention.

FIG. 12 is a cross-sectional view of a light emitting diode encapsulatedwithin a polymeric layer having a nanocrystal density gradient inaccordance with one embodiment of the present invention.

FIG. 13 is a traditional LED chip—silicon cap assembly.

FIG. 14 is a nanocomposite—LED chip assembly in accordance with oneembodiment of the present invention.

FIG. 15 is a nanocomposite—LED chip assembly in accordance with oneembodiment of the present invention.

FIG. 16 is a plot of percent transmittance for a silicone nanocompositecomprising ZnS nanocrystals as a function of nanocrystals size.

FIG. 17 is a plot of percent transmission for a silicone nanocompositecomprising ZnS nanocrystals as a function of wavelength.

FIG. 18 shows a representation of a 3-part ligand, with a tail-group, ahead group and a middle/body-group.

FIG. 19 is an example ligand that can be conjugated to the nanocrystalsof the present invention.

FIGS. 20 a-20 n show examples, chemical synthesis, and NMRcharacterization of several example ligands in accordance with thepresent invention.

FIG. 21 is a flowchart depicting processes for preparing polymericlayers in accordance with the present invention.

FIG. 22 is a cross-sectional view of a polymeric layer comprisingindividual layers each with a different nanocrystal density gradientaccording to one embodiment of the present invention.

FIG. 23 shows an X-Ray diffraction analysis of ZnS nanocrystals.

FIG. 24 shows Transmission Electron Micrographs of ZnS nanocrystals.

FIG. 25 A-B schematically illustrate chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 26 schematically illustrates chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 27 schematically illustrates chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 28 schematically illustrates chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 29 schematically illustrates chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 30 schematically illustrates chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 31 A-C schematically illustrate chemical synthesis of an exemplaryligand in accordance with the present invention.

FIG. 32 presents a photoluminescence spectrum of a typical InP/ZnSnanocrystal sample with green emission. The FWHM of the spectrum isindicated.

FIG. 33 Panel A presents absorption spectra of fluorescein dye. Panel Bpresents photoluminescence spectra of the dye. Panel C presents anabsorption spectrum of the InP/ZnS nanocrystals of FIG. 32. Panel Dpresents a photoluminescence spectrum of the nanocrystals. Panel E showsthe quantum yield deduced from Panels A-D.

The present invention will now be described with reference to theaccompanying drawings. In the drawings, like reference numbers indicateidentical or functionally similar elements.

DETAILED DESCRIPTION

It should be appreciated that the particular implementations shown anddescribed herein are examples of the invention and are not intended tootherwise limit the scope of the present invention in any way. Indeed,for the sake of brevity, conventional electronics, manufacturing,semiconductor devices, and nanocrystal, nanowire (NW), nanorod,nanotube, and nanoribbon technologies and other functional aspects ofthe systems (and components of the individual operating components ofthe systems) may not be described in detail herein. It should further beappreciated that the manufacturing techniques described herein can beused to create any semiconductor device type, and other electroniccomponent types. Further, the techniques would be suitable forapplications in electrical systems, optical systems, consumerelectronics, industrial or military electronics, wireless systems, spaceapplications, or any other application.

The present invention provides various polymeric nanocompositescomprising polymeric materials with embedded nanocrystals. The variousproperties of the nanocrystals, including their absorption properties,emission properties and refractive index properties, are utilized tocreate nanocomposites that can be tailored and adjusted for variousapplications. In one embodiment, the present invention providesapplications of semiconductor nanocrystals that utilize their emissionproperties in down-conversion applications. In another embodiment, thepresent invention combines two, non-electronically active properties ofthe same nanocrystals, by using the high absorption coefficient andrelatively sharp band edge of the nanocrystals to filter light as acutoff filter. In another embodiment, the high refractive index ofnanocrystals can also be used when mixed into low refractive indexmaterials to create substantially transparent nanocomposites witheffective refractive indexes matched to the substrates they are coating.In further embodiments, the refractive index of the nanocomposite can bematched to a second, further encapsulating material. The presentinvention also provides for nanocomposites that combine two or more ofthese various properties in different configurations into the samenanocomposite.

One aspect of the present invention provides novel nanostructureligands, including, for example, ligands that enhance the miscibility ofnanostructures in solvents or polymers, increase quantum efficiency ofnanostructures, and/or preserve nanostructure luminescence when thenanostructures are incorporated into a matrix. Other aspects providemethods of making indium phosphide nanostructures and core-shellnanostructures, as well as nanostructures having high quantumefficiency, small size, and/or a narrow size distribution.

As used herein, the term “nanocrystal” refers to nanostructures that aresubstantially monocrystalline. A nanocrystal has at least one region orcharacteristic dimension with a dimension of less than about 500 nm, anddown to on the order of less than about 1 nm. As used herein, whenreferring to any numerical value, “about” means a value of ±10% of thestated value (e.g. about 100 nm encompasses a range of sizes from 90 nmto 110 nm, inclusive). The terms “nanocrystal,” “nanodot,” “dot” and“quantum dot” are readily understood by the ordinarily skilled artisanto represent like structures and are used herein interchangeably. Thepresent invention also encompasses the use of polycrystalline oramorphous nanocrystals.

Typically, the region of characteristic dimension will be along thesmallest axis of the structure. Nanocrystals can be substantiallyhomogenous in material properties, or in certain embodiments, can beheterogeneous. The optical properties of nanocrystals can be determinedby their particle size, chemical or surface composition. The ability totailor the nanocrystal size in the range between about 1 nm and about 15nm enables photoemission coverage in the entire optical spectrum tooffer great versatility in color rendering. Particle encapsulationoffers robustness against chemical and UV deteriorating agents.

Nanocrystals for use in the present invention can be produced using anymethod known to those skilled in the art. Suitable methods are disclosedin U.S. patent application Ser. No. 10/796,832, filed Mar. 10, 2004, nowabandoned. U.S. patent application Ser. No. 10/656,910, filed Sep. 4,2003, which issued on Sep. 27, 2005, as U.S. Pat. No. 6,949,206, andU.S. Provisional Patent Application No. 60/578,236, filed Jun. 8, 2004,the disclosures of each of which are incorporated by reference herein intheir entireties. The nanocrystals for use in the present invention canbe produced from any suitable material, suitably an inorganic material,and more suitably an inorganic conductive or semiconductive material.Suitable semiconductor materials include those disclosed in U.S. patentapplication Ser. No. 10/796,832 and include any type of semiconductor,including group II-VI, group III-V, group IV-VI and group IVsemiconductors. Suitable semiconductor materials include, but are notlimited to, Si, Ge, Sn, Se, Te, B, C (including diamond), P, BN, BP,BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb,AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS,CdSe, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe,GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, CuI,Si₃N₄, Ge₃N₄, Al₂O₃, (Al, Ga, In)₂ (S, Se, Te)₃, Al₂CO, and anappropriate combination of two or more such semiconductors.

In certain aspects, the semiconductor nanocrystals may comprise a dopantfrom the group consisting of: a p-type dopant or an n-type dopant. Thenanocrystals useful in the present invention can also comprise II-VI orIII-V semiconductors. Examples of II-VI or III-V semiconductornanocrystals include any combination of an element from Group II, suchas Zn, Cd and Hg, with any element from Group VI, such as S, Se, Te, Po,of the Periodic Table; and any combination of an element from Group III,such as B, Al, Ga, In, and Tl, with any element from Group V, such as N,P, As, Sb and Bi, of the Periodic Table.

Other suitable inorganic nanostructures include metal nanostructures.Suitable metals include, but are not limited to, Ru, Pd, Pt, Ni, W, Ta,Co, Mo, Ir, Re, Rh, Hf, Nb, Au, Ag, Ti, Sn, Zn, Fe, FePt, and the like.

The nanocrystals useful in the present invention can also furthercomprise ligands conjugated, cooperated, associated or attached to theirsurface as described throughout. Suitable ligands include any groupknown to those skilled in the art, including those disclosed in U.S.patent application Ser. No. 10/656,910, which issued on Sep. 27, 2005,as U.S. Pat. No. 6,949,206, and U.S. Provisional Patent Application No.60/578,236. Use of such ligands can enhance the ability of thenanocrystals to incorporate into various solvents and matrixes,including polymers. Increasing the miscibility (i.e., the ability to bemixed without separation) of the nanocrystals in various solvents andmatrixes allows them to be distributed throughout a polymericcomposition such that the nanocrystals do not aggregate together andtherefore do not scatter light. Such ligands are described as“miscibility-enhancing” ligands herein.

As used herein, the term nanocomposite refers to matrix materialscomprising nanocrystals distributed or embedded therein. Suitable matrixmaterials can be any material known to the ordinarily skilled artisan,including polymeric materials, organic and inorganic oxides.Nanocomposites of the present invention can be layers, encapsulants,coatings or films as described herein. It should be understood that inembodiments of the present invention where reference is made to a layer,polymeric layer, matrix, or nanocomposite, these terms are usedinterchangeably, and the embodiment so described is not limited to anyone type of nanocomposite, but encompasses any matrix material or layerdescribed herein or known in the art.

I. Down-Converting Nanocomposites

In order to become competitive with traditional lighting fromfluorescent and incandescent lights, significant improvements must bemade in solid-state white lighting (SSWL). Improvements not just in thequantum efficiency of the phosphors, but in all aspects of thedown-conversion system that relate to efficiency, color-rendering andoverall system cost are needed. In one embodiment, the present inventionprovides a complete down-conversion system based on engineerednanocomposite materials for use with currently available blue LEDexcitation sources that dramatically improve the overall cost,performance and efficiency of SSWL. The down-converting nanocompositesof the present invention utilize the emission properties of nanocrystalsthat are tailored to absorb light of a particular wavelength and thenemit at a second wavelength, thereby providing enhanced performance andefficiency of active sources (e.g., LEDs). As such, the nanocrystalsutilized in the down-converting applications of the present inventionwill be constructed and tailored so as to be highly emitting. In oneembodiment, this system produces SSWL that exceeds performance of thebest traditional fluorescent and incandescent bulbs, with colorrendering of greater than 80 and power efficiency of greater than 200lm/W, at a cost of less than one U.S. dollar/klm.

Performance Characteristics of SSWL Devices

To evaluate the performance characteristics of solid-state whitelighting (SSWL) devices, three primary attributes are commonly used: (1)luminous efficiency, (2) Correlated Color Temperature (CCT) and (3)Color Rendering Index (CRI). DOE and Optoelectronics IndustryDevelopment Association “Light emitting diodes (LEDs) for generalillumination,” Technology Roadmap (2002).

The luminous efficiency (measured in lm/W) is the efficiency of theconversion from electrical power (W) to optical power (W), combined withthe efficiency of the conversion from optical power (W) to the luminousflux. The luminous efficiency is influenced by a number of factors, andcan, in general terms, be written as a contribution of several separateefficiencies:E _(luminous)=η_(wp)×η_(lum)×η_(ss)×η_(IQE)×η_(package)(E _(os) ,E _(pa),E _(TIR) ,E _(exp))× . . .where η_(wp) is the wall plug efficiency, η_(lum) is the photopicefficiency/response of the human eye, η_(ss) is the stokes shiftefficiency from converting a blue photon to a longer wavelength photon,η_(IQE) is the internal quantum efficiency of the phosphor, andη_(package) is overall package efficiency and accounts for losses inlight extraction efficiency from optical scattering (E_(os)), parasiticscattering (E_(ps)), total internal reflection (E_(TIR)), externalpackaging like the lead frame and submount (E_(exp)), etc.

CCT or correlated color temperature refers to the human eye property ofbeing optimally adapted to the sunlight spectral content. The relativeintensities of the blue (B), red (R) and green (G) colors, for thedesired white color, referred to as chromaticity coordinates, optimallyreproduce those in the visible sunlight, which corresponds to ablackbody spectral distribution of 6000 Kelvin (K). For optimumillumination the chromaticity coordinates for R, G and B must fall nearthe black body radiation, for temperatures between 2000° C. and 8000° C.Higher or lower than “optimum” temperatures register to the eye as too“cold” or too “warm” color hues.

Color rendering has to do with the appearance of various object colorsunder a given source illumination, compared to that from a referencesource. A collection of 14 sample colors of different saturation iscustomarily used for the color rendering index (CRI), which provides aquantitative measure on a scale of 1 to 100. Two sources of similarcolor temperature may produce widely varying CRIs. Low CRIs make colorsunacceptable for illumination, while high CRI (>80) are acceptable forgeneral illumination purposes.

Procedure for Providing an Optimized White Light Emitting Device

In one embodiment, the present invention provides processes comprising:

(1) A simulation model can be used to determine optimized nanocrystalmixtures for CRI, CCT, and luminous efficiency with targets of CRI>80,CCT about 4,000 K and efficiency of 200 lm/W.

(2) Nanocrystals and nanocrystal component mixtures are synthesized withemission peak widths, peak maximums, and intensity ratios determined bysimulation.

(3) A controlled nanocrystal phosphor nanocomposite is developed,including: (a) a surface ligand capable of achieving high (about 20% ormore) loading density in the selected composite is produced; (b) aligand exchange process to incorporate a 3-part ligand onto thenanocrystal is performed; (c) a homogeneous, non-phase separated TiO₂nanocomposite with nanocrystal loading densities up to 20% by volume isproduced; (d) quantum yield (QY) dependence on nanocrystal loadingdensity in the nanocomposite is determined; (e) an index of refractiondependence on loading density in the nanocomposite and index-matching ofthe nanocomposite to blue LED substrate (e.g., sapphire and/or SiC) isdetermined; and (f) a relationship of loading density and film thicknessto optimize refractive index matching and nanocomposite optical densityis determined.

Simulations for Determining Optimum Nanocrystal Component Mixture forHigh Color Rendering, Color Temperature and High Efficiency

In order to predict and maximize CRI, CTT and luminous efficiency ofnanocrystal mixtures, a dynamic and robust simulation model is used. Asuper-convergent, random-search, parameter optimization algorithm isused to find the maximum performance point, subject to the imposedconstraints. The model allows calculation of these performancecharacteristics based on actual experimental colorimetric and opticalcharacteristics of nanophosphor components and mixtures. In turn, thismodel is used to aid the design and fabrication of optimal nanocompositeSSWL devices.

The simulation program incorporates an algorithm to determine theoptimum spectral emission characteristics of nanocrystal componentmixtures for simultaneous maximization of color rendering, colortemperature and overall efficacy for production of white light. Theapproach provides a super-convergent, random search, optimizationalgorithm in the phosphor parameter space. The program seeks acombination of emission wavelengths that simultaneously maximizesluminous efficacy, color rendering (CRI) and color temperature (CCT),subject to the white-light chromaticity constrains calculated usingstandard CIE (Commission Internationale de l'Eclairage). The measurednanocrystal quantum efficiency, peak wavelength and emission spectralwidth are input parameters. Performance boundaries, as for example,efficacy no less than 90%, or CRI>90, can also be applied forflexibility in the design. The number of required wavelengths (i.e.,nanocrystal sizes) is a variable that allows a determination oftrade-offs between performance and manufacturing cost.

A validation procedure with iteration cycles is adopted, wherebymixtures of nanocrystal components, of size, composition peak maximum,peak widths, mixture abundance, and internal quantum efficiencypredicted by the simulation are manufactured. The resulting values ofCRI and CCT are determined experimentally and compared with thepredictions and adjustments are made as appropriate. The luminousefficiency is determined based on optical parameters including stokeshift efficiency, internal quantum efficiency and photopic response.

The output of this procedure is the optimum number of emission colors,the precise center wavelengths of each color, the precise spectral widthof each color and the exact relative intensity of each and thecorresponding concentration based on excitation by, for example, aselected blue LED (about 460 nm).

The simulations described throughout can determine suitable emissioncharacteristics for the nanocrystal. In addition, it is useful to (1)synthesize the materials with the prescribed spectral characteristicsand (2) use the materials to validate the model. To achieve thisobjective, available solution phase synthetic techniques are used tofabricate core/shell nanocrystal phosphors and characterize mixtures asdetermined by the theoretical model.

Based on current methods, nanocrystal batches are fabricated withspectral characteristics generated by the theoretical model. Eachdistinct wavelength is synthesized separately and combined to producethe final mixture. Specific attention is paid to the center wavelengthand the peak-width of each sample. In particular, narrow emission in thered avoids efficiency loss in the IR. In order to accomplish this, asolution-phase mixture of nanocrystals is produced and characterizedthat has the appropriate composition to produce white light with CRI andCTT, matching that of the theoretical model when illuminated with blueexcitation and total down-conversion efficiency comparable to thatpredicted by the model, assuming zero loss to other mechanisms in theprocess. These measurements can be made in the solution-phase using astandard visible fluorometer and fluorescence standards with excitationmatching the blue-LED.

Nanocrystal Phosphors

While any method known to the ordinarily skilled artisan can be used tocreate nanocrystal phosphors, suitably, a solution-phase colloidalmethod for controlled growth of inorganic nanomaterial phosphors isused. See Alivisatos, A. P., “Semiconductor clusters, nanocrystals, andquantum dots,” Science 271:933 (1996); X. Peng, M. Schlamp, A.Kadavanich, A. P. Alivisatos, “Epitaxial growth of highly luminescentCdSe/CdS Core/Shell nanocrystals with photostability and electronicaccessibility,” J. Am. Chem. Soc. 30:7019-7029 (1997); and C. B. Murray,D. J. Norris, M. G. Bawendi, “Synthesis and characterization of nearlymonodisperse CdE (E=sulfur, selenium, tellurium) semiconductornanocrystallites,” J. Am. Chem. Soc. 115:8706 (1993). This manufacturingprocess technology leverages low cost processability without the needfor clean rooms and expensive manufacturing equipment. In these methods,metal precursors that undergo pyrolysis at high temperature are rapidlyinjected into a hot solution of organic surfactant molecules. Theseprecursors break apart at elevated temperatures and react to nucleatenanocrystals. After this initial nucleation phase, a growth phase beginsby the addition of monomers to the growing crystal. The result isfreestanding crystalline nanoparticles in solution that have an organicsurfactant molecule coating their surface.

Utilizing this approach, synthesis occurs as an initial nucleation eventthat takes place over seconds, followed by crystal growth at elevatedtemperature for several minutes. Parameters such as the temperature,types of surfactants present, precursor materials, and ratios ofsurfactants to monomers can be modified so as to change the nature andprogress of the reaction. The temperature controls the structural phaseof the nucleation event, rate of decomposition of precursors, and rateof growth. The organic surfactant molecules mediate both solubility andcontrol of the nanocrystal shape. The ratio of surfactants to monomer,surfactants to each other, monomers to each other, and the individualconcentrations of monomers strongly influence the kinetics of growth.

In suitable embodiments, CdSe is used as the nanocrystal material, inone example, for visible light down-conversion, due to the relativematurity of the synthesis of this material. Due to the use of a genericsurface chemistry, it is also possible to substitutenon-cadmium-containing nanocrystals.

Core/Shell Nanocrystals

In semiconductor nanocrystals, photo-induced emission arises from theband edge states of the nanocrystal. The band-edge emission fromnanocrystals competes with radiative and non-radiative decay channelsoriginating from surface electronic states. X. Peng, et al., J. Am.Chem. Soc. 30:7019-7029 (1997). As a result, the presence of surfacedefects such as dangling bonds provide non-radiative recombinationcenters and contribute to lowered emission efficiency. An efficient andpermanent method to passivate and remove the surface trap states is toepitaxially grow an inorganic shell material on the surface of thenanocrystal. X. Peng, et al., J. Am. Chem. Soc. 30:7019-7029 (1997). Theshell material can be chosen such that the electronic levels are type Iwith respect to the core material (e.g., with a larger bandgap toprovide a potential step localizing the electron and hole to the core).As a result, the probability of non-radiative recombination can bereduced.

Core-shell structures are obtained by adding organometallic precursorscontaining the shell materials to a reaction mixture containing the corenanocrystal. In this case, rather than a nucleation-event followed bygrowth, the cores act as the nuclei, and the shells grow from theirsurface. The temperature of the reaction is kept low to favor theaddition of shell material monomers to the core surface, whilepreventing independent nucleation of nanocrystals of the shellmaterials. Surfactants in the reaction mixture are present to direct thecontrolled growth of shell material and ensure solubility. A uniform andepitaxially grown shell is obtained when there is a low lattice mismatchbetween the two materials. Additionally, the spherical shape acts tominimize interfacial strain energy from the large radius of curvature,thereby preventing the formation of dislocations that could degrade theoptical properties of the nanocrystal system.

In suitable embodiments, ZnS can be used as the shell material usingknown synthetic processes, resulting in a high-quality emission. Asabove, if necessary, this material can be easily substituted if the corematerial is modified.

Optical Properties of Core-Shell Nanocrystals

Due to the finite size of the core-shell nanocrystals, they displayunique optical properties compared to their bulk counterparts. Theemission spectrum is defined by a single Gaussian peak, which arisesfrom the band-edge luminescence. The emission peak location isdetermined by the core particle size as a direct result of quantumconfinement effects. For instance, by adjusting the particle diameter inthe range of 2 nm and 15 nm, the emission can be precisely tuned overthe entire visible spectrum (FIG. 1). FIG. 1 represents the absorptionand emission peaks for nanocrystals of increasing size (2 nm to 15 nm).The initial peak (lower wavelength) indicates the absorption wavelengthand the later peak (higher wavelength) the emission wavelength in nm.With increasing size of the nanocrystals, the absorption and emissionpeak wavelengths shift from about 450 nm to about 700 nm, and can betuned over this range. The vertical shaded bars on FIG. 1 indicatevisible light wavelengths in the blue 100, green 102 and red 104 ranges.

The width of the emission peak is determined by the size distribution ofthe sample. Peak widths down to 20 nm full width at half maximum (FWHM)can be achieved. Conversely, the absorption spectrum of nanocrystals isvery broad and intense, as typical of the bulk material, which ischaracteristically different than organic phosphors. Absorptioncoefficients are in excess of 55,000/cm (in the blue range of thespectrum) over the entire range of crystal sizes. In addition,core-shell nanocrystals can be made with quantum efficiencies as high as90% (this does not take into account energy loss due to Stokes shift,but is simply the ratio of photons-out to photons-in).

In one embodiment, the present invention provides an engineerabledown-converting system (see FIG. 2). Systems according to the presentinvention can comprise a nanocomposite down-converting layer that can becoated directly onto an LED wafer prior to dicing and packaging,eliminating the need for heterogeneous integration of the phosphor layerduring packaging. The nanocomposite down-converting layer is suitablyengineered from three components, including: (1) Semiconductornanocrystal phosphors of one or more, suitably two or more, sizes tunedto emit at the required wavelength(s) and with the required spectralcharacteristics to optimize the color rendering index (CRI) and powerconversion efficiency in the final device; (2) A host matrix (e.g., apolymer) selected for high index of refraction (generally about 1.5 orgreater), low UV degradation and matched thermal expansion to the LEDchip; and, (3) A unique nanocrystal surface chemistry that acts as theinterface between the nanocrystals and the host matrix, allowing eachelement to be independently selected and tailored without impacting theother component. As shown in FIG. 2, such a down-convertingnanocomposite phosphor layer 208 will take the place of phosphor 200 andphosphor encapsulant layer 206.

By independently selecting and tuning each of these three components, itis possible to simultaneously: (1) engineer a specific compositeemission spectrum that can be tailored to optimize between CRI anddown-conversion efficiency; (2) refractive index match the compositelayer to the LED chip to reduce light-extraction losses prior to downconversion; (3) reduce scattering in the down-conversion layer, therebyminimizing light-extraction losses from the phosphor layer; (4) producedown-conversion with a quantum efficiency greater than about 20% (e.g.,40%, 60%, 80%, 100%) at any wavelength with simultaneous and efficientabsorption of light (about 300 nm) (depending upon size and compositionof the nanoparticles); and (5) minimize loss of efficiency due tophotons emitted into the near-infra-red (near-IR) through the use ofextremely sharp emission spectra in red light wavelengths (about 20 nmFWHM). This approach makes it possible to achieve overallpower-conversion efficiencies greater than 200 lm/W, with CRI greaterthan 80, and overall chip brightness of greater than 100 Watts/chip at acost of less than one U.S. dollar/klm.

Nanocomposite System Features Benefit to SSWL High quantum efficiency Noloss of photons upon down (as high as 90%) conversion resulting in2-fold increase in overall power-conversion efficiency over traditionalphosphors. Continuous, tunable The emission peak wavelength and widthemission spectrum can be precisely tuned so mixtures of different sizednanocrystals can be formed with precise emission characteristics toachieve maximum emission efficiency, CRI, CTT. Narrow and Sharp EmissionSharp emission allows tailoring of emitted light at wavelengths wherethe luminous efficiency of photopic vision of the eye is high. Highphoto- and chemical Nanocrystals are not susceptible to stabilitybleaching effects and environmental sensitivities (UV, moisture, oxygen)as traditional organic phosphors offering long operating lifetimes.Mixtures of nanocrystals Mixtures of nanocrystals can be in host matrixembedded in a host matrix of virtually any material at high-loadingdensities (e.g., 20% by volume) with precise control over relativeconcentration ratios through modification of surface chemistry.Non-scattering composites Due to the small particle size and capabilityto make homogenous dispersion of the nanocrystals, optical scattering aswell as parasitic absorption can be minimized or eliminated to improvelight extraction efficiency and hence the device luminous efficiency.Tunable refractive index By selecting the proper host matrix materialand tailoring the loading density, the index of refraction of thenanocomposite layer can be precisely tuned from about 1.5 to about 2.5to minimize or even eliminate total internal reflection at theLED-nanocomposite interface, potentially increasing overall powerconversion efficiency. Loading density and thickness can be traded- offto simultaneously optimize index of refraction and optical density ofthe composite layer while maintaining film thicknesses. High absorptionAt a high loading density, the coefficients nanocompositedown-conversion layer (as high as 55,000/cm) can be on the order of asingle micron in thickness. This allows direct incorporation at thewafer-level using traditional thin film processing, dramaticallyreducing overall manufacturing costs for SSWL relative to thick-filmphosphor layers that are incorporated at the package level.

FIG. 3 illustrates the emission range of the down-convertingnanocomposites of the present invention, in the red region of a 2-colorphosphor mix, compared to that resulting from traditional inorganicphosphors for white. Emission peaks 302 and 304 represent the emissionspectra of a 2-color phosphor mix according to one embodiment of thepresent invention. Spectrum 306 represents the emission spectrum oftraditional inorganic phosphors. Not only does the narrow emissionprevent photon waste at the edges of the visible spectrum by the eye,but it also allows a superior optimization of color rendering index andpower conversion efficiency. Wasted light region 308 demonstrates lightemitted from traditional inorganic phosphors at the edges of the visiblespectrum that is cut out by using the sharp emission peak 304.

FIG. 4 illustrates the concept of fine-tuning the emission by using morethan three emission colors, each with a specific, narrow, emission peak,to generate an overall emission spectrum with a superior color renderingindex that can be as high as 100 for any color temperature. Between thetwo extremes of extremely broad emission and extremely narrow emission,however, is a balance between efficiency and CRI. The exact number ofcolors, center wavelengths, relative concentrations and spectral widthscan be determined theoretically to optimize both parameterssimultaneously.

By using standard thin-film and lithographic processing techniques, asshown in FIG. 5, green 500 and red 502 down-conversion layers can bepatterned across LED chips 204 prior to dicing. This allows low-costfabrication of 3-color emitting LEDs integrated into a single die, suchthat a single chip can be used to dynamically tune emission of the LEDfrom monochromatic to white for any color temperature. As such, thepresent invention provides formation of an integrated chip-level 3-colormixing-based SSWL for all lighting applications, at a cost pointcompetitive with traditional lighting, but with far superior efficiency,performance and color engineering capability.

Suitable matrixes for use in all embodiments of the present inventioninclude polymers and organic and inorganic oxides. Suitable polymers foruse in the matrixes of the present invention include any polymer knownto the ordinarily skilled artisan that can be used for such a purpose.In suitable embodiments, the polymer will be substantially translucentor substantially transparent. Such polymers include, but are not limitedto, poly(vinyl butyral):poly(vinyl acetate), silicone and derivatives ofsilicone, including, but not limited to, polyphenylmethylsiloxane,polyphenylalkylsiloxane, polydiphenylsiloxane, polydialkylsiloxane,fluorinated silicones and vinyl and hydride substituted silicones.

The nanocrystals used the present invention can be embedded in apolymeric (or other suitable material, e.g., waxes, oils) matrix usingany suitable method, for example, mixing the nanocrystals in a polymerand casting a film, mixing the nanocrystals with monomers andpolymerizing them together, mixing the nanocrystals in a sol-gel to forman oxide, or any other method known to those skilled in the art. As usedherein, the term “embedded” is used to indicate that the nanocrystalsare enclosed within the polymer that makes up the majority component ofthe matrix.

The thickness of the layers of the present invention can be controlledby any method known in the art, such as spin coating and screenprinting. Such methods are especially useful when coating opticaldevices such as lenses or mirrors with the polymeric layers. While thevarious polymeric layers of the present invention can be any thicknessrequired, suitably, the layers will be less than about 100 mm inthickness, and down to on the order of less than about 1 mm inthickness. In other embodiments, the polymeric layers of the presentinvention can be on the order of 10's to 100's of microns in thickness.In one embodiment, the present invention provides nanocrystal dopedlayers that are greater than about 0.5 mm in thickness, and suitablywill scatter only a minimal portion of light that enters the layer (seelater for a discussion of scattering). In other embodiments, the layerswill be between about 0.5 mm and about 50 mm in thickness. In allembodiments of the present invention, the nanocrystals can be embeddedin the various matrixes at any loading ratio that is appropriate for thedesired function. Suitably, the nanocrystals will be loaded at a ratioof between about 0.001% and about 75% by volume depending upon theapplication, matrix and type of nanocrystals used. The appropriateloading ratios can readily be determined by the ordinarily skilledartisan and are described herein further with regard to specificapplications.

II. Photon-Filtering Nanocomposites

In another embodiment, the present invention provides polymeric layerscomprising a polymer and nanocrystals embedded within the polymer, suchthat the layers act as photon-filtering nanocomposites. Suitably, thenanocrystals will be prepared from semiconductor materials, but anysuitable material described throughout can be used to prepare thenanocrystals. In certain embodiments, the nanocrystals will have a sizeand a composition such that the nanocrystals absorb light of aparticular wavelength or over a range of wavelengths. As such, thenanocrystals utilized in these embodiments are tailored such that theirabsorption characteristics are enhanced or maximized, while theiremission characteristics are minimized, i.e. they will absorb light in ahighly efficient manner, but suitably will emit only a very low level,or preferably no light. In other embodiments, however, thephoton-filtering nanocomposites can also comprise nanocrystals that havehigh emission properties and emit light at a particular wavelength asdiscussed throughout. As such, the present invention providesnanocomposites that comprise different types of nanocrystals such thatthe nanocomposites exhibit several, or all, of the properties discussedthroughout, in a layer.

A photon-filtering nanocomposite in accordance with one embodiment ofthe present invention is shown in FIG. 6. FIG. 6 is a cross-sectionalview of a polymeric layer 600 showing nanocrystals 604 embedded inpolymer 602. Note that nanocrystals 604 are not to scale and are visiblyrepresented for illustrative purposes only. The polymeric layers andnanocomposites of the present invention can also comprise nanocrystalsof different sizes and compositions within the same layer.

In suitable embodiments, the nanocrystals can be distributedhomogenously throughout the polymeric layer and nanocomposites (see FIG.6). In other embodiments, the nanocrystals can be randomly distributed.In further embodiments, the nanocrystals can be distributed throughoutthe layer such that they form a nanocrystal density gradient throughoutthe layer (as discussed further in the refractive index section below).Such an embodiment is represented in FIG. 7, which shows across-sectional view of a polymeric layer 700 with nanocrystals 604embedded in polymer 602 in such a way that they form a nanocrystaldensity gradient from high density (lower portion of FIG. 7) to lowdensity (upper portion of FIG. 7) within polymer 602.

The photon-filtering polymeric layers and nanocomposites of the presentinvention can be used to coat, encapsulate, cover, be deposited on (orany other similar arrangement known to those skilled in the art) anysubstrate material. Suitably, the polymeric layers of the presentinvention can be used to coat optical devices. In other embodiment, thepolymeric layers can be used to encapsulate active devices.

In embodiments of the present invention where the photon-filteringpolymeric layers are used to coat optical devices, such optical devicescan be refractive (e.g., lenses) or reflective (e.g., mirrors). FIG. 8is a cross-sectional view of an optical device 802 coated with polymer602 comprising nanocrystals 604. Coated optical devices 800 according tosuch an embodiment can be used in any application where a filter oranti-reflective coating is desired on a refractive or reflective device.

In embodiments of the present invention where the photon-filteringpolymeric layers are used to encapsulate active devices, such activedevices can be any device known to the skilled artisan. As used hereinan “active device” is one that requires a source of energy for itsoperation and has an output that is a function of present and past inputsignals. Examples of active devices include, but are not limited to,controlled power supplies, transistors, diodes, including light emittingdiodes (LEDs), light detectors, amplifiers, transmitters and othersemiconductor devices.

By controlling the size and composition of the nanocrystals used in thepractice of the present invention, the nanocrystals will absorb light ofa particular wavelength, or a particular range of wavelengths, while notscattering light. The ability to make nanocrystals out of differentsemiconductors, and control their size, allows for polymeric layers tobe fabricated with nanocrystals that will absorb light from the UV, tovisible, to near infrared (NIR), to infrared (IR) wavelengths.Nanocrystals for use in the present invention will suitably be less thanabout 100 nm in size, and down to less than about 2 nm in size. Insuitable embodiments, the nanocrystals of the present invention absorbvisible light. As used herein, visible light is electromagneticradiation with wavelengths between about 380 and about 780 nanometersthat is visible to the human eye. Visible light can be separated intothe various colors of the spectrum, such as red, orange, yellow, green,blue, indigo and violet. The photon-filtering nanocomposites of thepresent invention can be constructed so as to absorb light that makes upany one or more of these colors. For example, the nanocomposites of thepresent invention can be constructed so as to absorb blue light, redlight, or green light, combinations of such colors, or any colors inbetween. As used herein, blue light comprises light between about 435 nmand about 500 nm, green light comprises light between about 520 nm and565 nm and red light comprises light between about 625 nm and about 740nm in wavelength. The ordinarily skilled artisan will be able toconstruct nanocomposites that can filter any combination of thesewavelengths, or wavelengths between these colors, and suchnanocomposites are embodied by the present invention.

Polymeric layers that comprise nanocrystals that can absorb light of aparticular wavelength, or range of wavelengths, will act as edge passfilters, absorbing light that is less than a certain wavelength. Forexample, the photon-filtering nanocomposites can be constructed so as toabsorb light that is less than about 565 nm (e.g., blue and green) andallowing wavelengths of light that are longer than about 565 nm (e.g.,red) to pass through the polymeric layer.

In other embodiments, the nanocrystals have a size and a compositionsuch that they absorb photons that are in the ultraviolet,near-infrared, and/or infrared spectra. As used herein, the ultravioletspectrum comprises light between about 100 nm to about 400 nm, thenear-infrared spectrum comprises light between about 750 nm to about 100μm in wavelength and the infrared spectrum comprises light between about750 nm to about 300 μm in wavelength.

While nanocrystals of any suitable material can be used in the practiceof the present invention, in certain embodiments, the nanocrystals canbe ZnS, InAs or CdSe nanocrystals. In one embodiment, InAs nanocrystals(with a 1340 nm absorption peak) with TOP (tri-n-octylphosphine) ligandsattached to their surface can be dissolved in a solvent such as toluene.Poly(vinyl butyral):poly(vinyl acetate) (PVB:PVA) polymer can also bedissolved in toluene and the two solutions can be mixed together. Asubstrate can then be coated or encapsulated with the mixture and thetoluene evaporated off. A thin film results that is non-light-scatteringdue to the size of the non-aggregated nanocrystals. Polymeric layersproduced in such a manner will have an effective refractive indexbetween that of either material by itself (i.e., the polymer or thenanocrystal material), which can be adjusted by modifying the loadingratio of the nanocrystals and the density of the nanocrystals at variouspoints in the polymeric layer (see Refractive Index section foradditional disclosure). A polymeric layer comprising such nanocrystalscan act as an antireflective filter, absorbing light that is less thanabout 1340 nm in wavelength.

In another embodiment of the present invention, CdSe nanocrystals(having an absorption peak at about 580 nm) with stearic acid ligandscan be dissolved in a solvent such as toluene. In other embodiments, ZnSnanocrystals with amine, carboxylic acid, phosphonic acid, phosphonate,phosphine, phosphine oxide or sulfur ligands can be dissolved in asolvent. In the case of CdSe nanocrystals, a ligand exchange can then beperformed in solution with a siloxane ligand and excess ligand can beremoved. Nanocrystals can then be mixed with a polymer base, such assilicone, and a substrate material can then be coated or encapsulated.After curing, the film will have an effective refractive index betweenthat of the polymer (e.g., silicone) and the nanocrystals, which can beadjusted by changing the loading ratio of the nanocrystals in thesilicone. Such a polymeric layer will act as a filter absorbing lightthat is less than about 580 nm in wavelength (i.e., blue, green, yellow,orange, violet, UV light).

III. Refractive Index Matching Nanocomposites

Poor extraction caused by total internal light reflection due to indexof refraction mismatches at interfaces is a problem for light emittingdevices, including LEDs. It is well known that light impinging aninterface between materials of index n and n′<n, at an angle θ relativeto the vertical will be totally reflected, if sin θ>sin θc=n′/n. For adirect extraction from GaN with n=2.26 into air n′=1, this limits theextraction cone within a solid angle ΔΩ2π(1−cos θc), where θc is thecritical extraction angle, θc=26°, being just 10% of the totalextraction angle 2π (upper half only). In the encapsulation arrangementshown in FIG. 2, overall light extraction relates to: (a) extractionfrom substrate 202 to phosphor encapsulant layer 206; and (b) fromphosphor encapsulant layer 206 to air. The radius of the encapsulantlayer is much larger than the emitting area (e.g., cm vs. mm) thus lightrays inside the encapsulant layer that reach out in the radial directionimpinge almost perpendicular to the encapsulant layer surface θ<<θc andare extracted. Thus the overall extraction is mainly limited byextraction from the substrate to the phosphor plane interface, takingadvantage of the higher phosphor critical angle, due to the higher thanair index of refraction.

In one embodiment, as shown in FIG. 2, the present invention providesnanocomposite layers 208, that can bond to LED substrate 202, that havean effective refraction index of greater than 1.5. In suitableembodiments, by increasing the substrate effective refractive index to1.8, an angle of θc=68′ is generated and the extraction efficiency isdoubled to 63%. In another embodiment, the present invention providesnanocomposites combining nanocrystals with a refractive index of about2.0 to about 3 with host matrix materials, including polymers (e.g.,TiO₂ with an effective refractive index 1.5 to 2, or silicone with arefractive index of about 1.49), to generate a nanocomposite materialwith an effective refractive index of about 2, with a criticalextraction angle of about θc=77°, thereby increasing the extractionefficiency to 78%. In further embodiments, a matched-index passive layer(e.g., a hard shell polymer) can be added above the phosphor layer totake advantage of the radial incidence, thereby enhancing extractionfrom the phosphor layer into the air.

As used herein, the term “effective refractive index (n_(e))” is used toindicate that the polymeric layers of the present invention arecomposite materials, and thus, their effective refractive index is aresult of the refractive index of all components of the layer. The termrefractive index as used herein indicates the degree to which thenanocomposites of the invention bend light. The refractive index of thenanocomposites can be determined by the ratio of the speed of light in avacuum divided by the speed of light in the nanocomposites.

The polymeric layers of the present invention, whether down-converting,photon-filtering, or refractive index matching, have an effectiverefractive index that can be controlled by the ratio, density,composition and size of the nanocrystals embedded within the matrix.FIG. 9 shows the effect of loading ratio of ZnS nanocrystals (n=2.35) onthe effective refractive index of various materials. For all matrixes,the effective refractive index increases linearly with the loading ratio(%) up to the refractive index of the pure ZnS nanocrystals. FIG. 10shows the effective refractive index of a silicone nanocompositecomprising 3 nm ZnS nanocrystals at 30% by volume as a function ofwavelength. An effective refractive index of greater than about 1.77 isobserved for all wavelengths from 300 nm to 700 nm.

Control and tailoring of the effective refractive index allows thematrixes of the present invention to be utilized in applications where alayer having either a uniform or varying effective refractive index maybe desired, for example as polymeric layers encapsulating LEDs. In suchapplications, a polymeric layer is used to encapsulate the lightemitting diode chip of an LED to provide protection to the chip. Asdiscussed above, due to refractive index (n) differences between thehigh n of the LED chip and the generally low n of the polymericencapsulant, large amounts of light are lost due to light reflecting atthe chip/polymer interface. The present invention therefore provides fora polymeric layer that has a refractive index higher than pure polymerthat can approach or match the refractive index of the LED chip, therebylimiting the light lost at the chip/polymer interface. Such anembodiment is represented in FIG. 11, showing a cross-sectional view ofan encapsulated light emitting diode 1100, in which polymer 602comprising embedded nanocrystals 604 encapsulates LED chip 1106. Anyactive device, including those discussed throughout, can be encapsulatedin a similar manner. Furthermore, FIGS. 11 and 12 showing specific LEDstructures are presented for illustrative purposes only, and any LEDstructure known to those skilled in the art can be similarlyencapsulated.

The effective refractive index of the polymeric layer can be any valuebetween that of the pure matrix material (e.g., silicone at about 1.49,TiO₂ at about 1.5) and the nanocrystals themselves (e.g., up to about3). Suitably, the effective refractive index of the matrix will begreater than about 1.5, preferably between about 1.5 and about 2.5, andin certain embodiments the refractive index of the matrix will be about1.8.

In other embodiments, in order to add further stability to an LEDstructure, a second polymeric layer can be added on top of the firstlayer. Often, this second layer will be a “hard-shell” polymer and willhave a refractive index that is lower than the LED chip. Thus, if therefractive index of the first polymeric layer is matched to therefractive index of the LED chip, reflections will occur at the firstpolymeric layer/hard shell polymer interface. In order to overcome thisproblem, in another embodiment, the present invention provides for apolymeric layer or polymeric encapsulant which has a density gradient ofnanocrystals such that the effective refractive index of the polymericlayer matches both the chip and the hard shell polymer at theirrespective interfaces.

In one such embodiment, the present invention provides polymeric layersthat encapsulate an active device that has an effective refractiveindex, n₁. The layer comprises a polymer and semiconductor nanocrystalsembedded within the polymer, and has an inner boundary in contact withthe active device and an outer boundary in contact with a medium thathas an effective refractive index, n₂. The layer has an effectiverefractive index less than or equal to n₁ at the inner boundary and aneffective refractive index greater than or equal to n₂ at the outerboundary. Suitably, the active device will be an LED, though any activedevice, including those described throughout, can be encapsulated. Insuitable embodiments, n₁ will be greater than n₂.

FIG. 12 shows a cross-sectional view of an LED encapsulated in such apolymeric layer. Encapsulated LED 1200 comprises polymeric layer 602comprising embedded nanocrystals 604 encapsulating LED chip 1106. Hardshell polymer 1202 further coats polymeric layer 602 to provideadditional structural integrity and protection to the LED. FIG. 12illustrates the nanocrystal density gradient throughout the thickness ofpolymeric layer 602, this gradient being highest at the boundary withLED chip 1106 and lowest at the boundary with hard shell polymer 1202.In such embodiments, the effective refractive index is n₁ at theboundary with LED chip 1106 and the effective refractive index is n₂ atthe boundary with hard shell polymer 1202. In certain embodiments, thisnanocrystal density gradient will be substantially linear throughout thepolymeric layer, though it can take any form throughout the thickness ofthe layer, e.g., cyclic, parabolic, etc. Suitably, the effectiverefractive index of polymeric layer 602 will be greater than about 1.5throughout the layer, and in certain embodiments will be about 1.8 (n₁)at the interface with LED chip 1106 and about 1.5 (n₂) at the interfacewith hard shell polymer 1202.

As shown in FIG. 13, light emitting diodes often utilize LED chip 1106covered by a drop or layer of silicone 1302 usually a few millimeters indiameter. As discussed throughout, by replacing the silicone cap in FIG.13 with nanocrystal doped matrixes with enhanced refractive indexes,more light can be extracted from LED chip 1106. However, two issues mayarise by doing so: (1) the amount of nanocrystals required for a dopedmatrix a few millimeters thick for each LED translates to rather largequantities of nanocrystals for mass production, thereby driving up thecost; and (2) the scattering from the nanocrystals throughout a thicklayer may make the matrix opaque for a path-length of a few millimeters.

To resolve these issues, in another embodiment (see FIG. 14), thepresent invention provides for a thin film of nanocomposite 1402 formedon the surface of an LED chip 1106, this thin film is then furthercapped with small hemispheres 1404 of the same nanocomposite. All of thelight that enters the nanocomposite hits the composite/air interface at90° and therefore does not suffer from any internal reflection. Thethickness of the film and the diameter of the small caps can be chosento satisfy the thermal compliance and other mechanical/thermalrequirements. The thickness, t, of the film, and the diameter, d, of thesmall hemispheres, can be in the range of 10's-100's of nms to micronsto millimeters. Suitably, the thickness of the layer will be on theorder of 10's of microns, for example about 10-50 microns. The diameterof the hemispheres is generally on the order of microns.

In other embodiments of the present invention, the small hemispheres1404 of nanocomposite can be further capped with a large hemisphere ofsilicone 1302, as illustrated in FIG. 15. In this case, the refractiveindex of the large hemisphere of silicone is not required for lightextraction. The critical angle is only determined by the refractiveindex of the LED chip 1106, n1, and that of the nanocrystal doped matrix(1402 and 1404), n3 as:

$\theta_{critical} = {\sin^{- 1}{\frac{n_{1}}{n_{3}}.}}$

Preparation of nanocomposite films and hemispheres in this manner allowsfor the use of larger sized nanocrystals in comparison to those that canbe used in conjunction with thicker pathlength films. For example,nanocrystals on the order of 5-7 nm could be used with the thinfilm/hemisphere embodiments of the present invention, while nanocrystalson the order of about 3-5 nm could be required for thicker pathlengthnanocomposites.

As discussed throughout, the nanocrystals useful in the practice of thepresent invention can have a composition and a size such that theyabsorb light at a particular wavelength(s) and emit at a particularwavelength(s). In certain embodiments, the polymeric layers of thepresent invention can comprise combinations of nanocrystals thatfunction in the various ways described herein. For example, ananocomposite of the present invention can comprise nanocrystals havingspecific, enhanced emission properties, others having specific, enhancedabsorption properties but low emission properties, and the entirenanocomposite can be constructed such that the layer has a specificrefractive index that is matched or tailored for a specific purpose.Combined in such a way, the polymeric layers of the present inventioncan be used as encapsulants for active devices (e.g., LEDs) that emitlight of a certain wavelength, filter out other wavelengths and have arefractive index appropriately matched to an active device and/or anadditional substrate or coating.

IV. Size and Miscibility of Nanocrystals

In all embodiments of the present invention, it is desirable that thenanocrystals do not aggregate. That is, that they remain separate fromeach other in the polymeric layer and do not coalesce with one anotherto form larger aggregates. This is important, as individual crystalswill not scatter light passing through the layer, while largeraggregated structures can create an opaque layer that can hinder thepassage of light.

Suitably, whether functioning as down-converting layers,photon-filtering layers, refractive index matching layers, orcombinations thereof, the nanocomposites of the present invention willscatter a minimal portion of light that enters the various layers. It isdesirable that the nanocomposites of the present invention scatter aslittle light as possible, such that the layers are substantiallytransparent or clear.

As used herein, the phrase “scatter a minimal portion of light,” meansthat the amount of light that enters the various nanocomposites of theinvention from the incident side (the side that light is entering) istransmitted such that less than about 50% of this incident light isscattered by the nanocomposite. In suitable embodiments, the amount oflight that is scattered by the nanocomposite will be less than about20%, less than about 15%, and approaching 0% of the light beingtransmitted. The factors that impact most significantly on the amount oflight that is scattered by the nanocomposites are the size of thenanocrystals and their miscibility in the polymeric matrix, and hencetheir ability to remain separated. It should be understood that inapplications of the present invention where the nanocomposites functionas filters, the amount of light that is transmitted through thepolymeric layer will necessarily be reduced as certain wavelengths orranges of wavelengths will absorbed by the nanocrystals and filtered outof the incident light.

As discussed above, the size of the nanocrystals can be tailored byselecting specific semiconductor materials and then generating andprocessing the nanocrystals until the desired size is attained. In thevarious embodiments of the present invention, the nanocrystals willsuitably be between about 1 nm and about 20 nm in size. More suitably,between about 1 nm and about 10 nm, between about 1 nm and about 4 nmand most suitably between about 1 nm and about 3 mm. As shown in FIG.16, using a constant loading volume of ZnS nanocrystals (22% by volume)in silicone, the percent transmittance of light can be tailored frombetween about 5% to about 100% (i.e. percent that is scattered can betailored from between about 95% to about 0%). It is a significantadvantage of the present invention that by generating nanocrystals thatare between about 1 nm to about 4 nm, less than about 50% of theincident light is scattered by the nanocomposites of the presentinvention. As shown in FIG. 16, by creating nanocrystals that arebetween about 1 nm and about 3 nm, scattering of less than 20%,approaching 15%, 10%, 5% and 0%, can be achieved. As demonstrated inFIG. 17, a silicone nanocomposite, comprising 3 nm ZnS nanocrystals anda layer with a 3 mm pathlength will scatter less than about 50% (i.e.transmit more than about 50%) of the incident light over the wavelengthrange 350 nm to 700 nm, scatter less than about 30% over the wavelengthrange 400 nm to 700 nm and scatter less than about 15% over thewavelength range 500 nm to 700 nm.

Controlled Surface Chemistry for High Loading Density Nanocomposites

In the formation of the nanocomposites of the present invention, twocritical issues are: (1) achieving high miscibility of the nanocrystalsin the host matrix, and (2) prevention of aggregation of thenanocrystals at a high concentration. Aggregation results in quenchingof the emission, hence a lowering of the amount of light transmitted, aswell as light scattering from the aggregates. Tuning the index ofrefraction of the overall composite layer also occurs at differentnanocrystals loading densities. Since the nanocrystals have a refractiveindex of about 2.5 to about 3 and the host matrix is about 1.5 to about2, matching of the refractive index of the LED substrate (typicallysapphire or SiC) will eliminate an optical interface and losses fromtotal internal reflection.

As part of this approach, several issues are addressed, includingdetermination of whether the necessary loading densities in thenanocomposites as determined by simulations are achieved; whether thenanocrystals are homogenously embedded in the host matrix with no (orminimized) aggregation or phase separation so that a high quantum yieldis retained and scattering is prevented; whether the index of refractionof the composite layer can be tuned by adjusting the loading density(e.g., gradient) of nanocrystals in the host matrix; whether refractiveindices close to the LED substrate are achieved and what the projectedeffect on the light extraction efficiency is; and at the nanocrystalloading density for refractive index matching, what is the layerthickness of the composite layer necessary to reach an optical densityat the excitation wavelength to yield the optimized emission profiledetermined by the simulations. It can also be determined whether thisthickness is compatible with low cost, thin film processing (e.g.,thicknesses <1-2 microns).

In order to accomplish this, a tailored, miscibility-enhancing ligandcan be designed to bind, associate, coordinate, attach or conjugate to ananocrystal, and to allow for controlled mixing and miscibility in thehost matrix. The performance characteristics, including quantifying theeffects on the internal quantum efficiency and light extractionefficiency are measured on nanocomposites of various loading densitiesand thicknesses.

Surface Chemistry Modification

Dispersion of nanocrystals in a host matrix can be controlled byminimizing phase separation and aggregation that can occur when mixingthe nanocrystals into the matrixes. A basic strategy of the presentinvention is to design a novel 3-part ligand, in which the head-group,tail-group and middle/body-group can each be independently fabricatedand optimized for their particular function, and then combined into anideally functioning complete surface ligand (see FIG. 18; see FIG. 19for an example ligand). As shown in FIG. 18, head group 1804 is selectedto bind specifically to the semiconductor or other material of thenanocrystal (e.g., can be tailored and optimized for CdSe, ZnS, a metal,or any other nanocrystal material). Tail group 1800 is designed tointeract strongly with the matrix material and be miscible in thesolvent utilized (and can, optionally, contain a linker group to thehost matrix) to allow maximum miscibility and loading density in thehost matrix without nanocrystal aggregation. Middle or body group 1802is selected for specific electronic functionality (e.g., chargeisolation).

This multipart ligand strategy has been used for the fabrication of highloading density, non-fluorescent, polymer-CdSe nanorod composites in thedevelopment of hybrid inorganic-organic nanocomposite solar cells. Incertain embodiments of the present invention, significant modificationsto the ligand are made due to differences in the two applications.Specifically, the ligand is designed to be charge insulating (ratherthan charge conducting) and to provide retention of nanocrystalphotoluminescence as well as to be compatible with a completelydifferent matrix type (inorganic rather than organic polymers) andnanocrystal material type and shape.

With the development of the 3-part ligand, control of the loadingdensity of the nanocrystals in the nanocomposite can be achieved forpurposes of creating the nanoparticle density gradients as described.This permits evaluation of the influence of quantum yield and opticalscattering in the nanocomposite. Additionally, tuning of the refractiveindex of the nanocomposite is possible since the index of refraction ofthe host matrix is known.

A benefit of this modular approach is the ability to rapidly evaluatenew tail, head, and middle/body groups. In the area of head groups(binding with the nanocrystal), there are available methods developedfor the development of CdSe synthetic techniques. This includes anunderstanding of the binding of nanocrystals with phosphonic acids,amines, thiols, phosphines, and phosphine oxides.

A tailored ligand can be optionally designed to bind strongly to thenanocrystal and to allow for mixing in a TiO₂ host medium. The newligand allows for dispersion control (solubility and processability) tofacilitate incorporation of the nanocrystals into solvents or hostmatrixes over a wide range of loading densities as necessary to achievethe optimal white light device performance characteristics andrefractive index matching to the blue-LED. Similarly, as other examples,ligands can be designed to bind strongly to the nanocrystal and allowfor mixing in a silicone or hydrocarbon polymer.

Ligand Synthesis

The ligand molecule can be synthesized using a generalized techniqueallowing three separate groups to be synthesized separately and thencombined. Head groups of phosphonic acid, amines, carboxylic acids orthiol moieties can be used because of their affinity for the nanocrystalsurface. Tail groups can contain terminal hydroxyl groups to tether thenanocrystal in a titania sol-gel matrix, silicon groups to match asilicone polymer matrix, or organic groups to match an organic matrix.The middle/body unit is selected, e.g., for charge insulation (e.g.,large energy gap for both electrons and holes), and possible targets areoptionally identified using computer modeling. The modeling is performedusing a Density Functional Theory (DFT) to model the bandgap of varioustarget molecular structures for ligand design. The confirmation of thechemical identity and purity will be done using mass spectrometry, NMRand FTIR analysis, or similar techniques.

The insulating group (middle/body unit) of the ligands can be selectedfrom long-chain alkanes of various lengths and aromatic hydrocarbons,e.g., C6-C22 alkanes. Selection of the length of the body unit willdepend on the desired characteristics of the final matrix and of thepolymeric base being used. For example, in applications where it isdesired that the matrix possess rheologic or other properties (e.g.,mechanical/electrical) similar to that of the polymeric base substance,a shorter chain (e.g., C6-C18) body unit can be selected. For example,the use of a C12 body unit-based ligand on ZnS nanocrystals allows forincreased loading of the ZnS nanocrystals at a ratio sufficient toachieve a refractive index of 1.7070 in a base of immersion oil(starting refractive index 1.5180), while still maintaining the greaselike consistency of the oil. The use of shorter chain ligands allows fora lower volume fraction of nanocrystals to be used to achieve the samerefractive index when compared to nanocrystals with longer chainligands.

In other applications, the use of longer chain ligands (e.g., C18-C22)can be used when it is desired that the final matrix possess propertiescloser to that of the ligand itself, rather than the base material. Incertain applications, the ligand itself could be used to form the matrixmaterial. Longer chain ligands also allow for additional spacing betweenthe nanocrystals to keep them from aggregating in the base substrate.

FIG. 19 shows an example of a ligand with a phosphonic acid head group1900, an aliphatic tail 1902 and an aromatic hydrocarbon body 1904.Appropriate choice of body and/or tail components are used to providelike functionality to the matrix to afford high concentrations ofnanocrystals in siloxane polymer matrices. Refractive index (RI)tuning/matching can also be affected by the ligand. Independent tuningof the tail or body components of the ligand to obtain a particular RImatch with the polymer matrix can be achieved by varying the ligandchemistry appropriately.

The general design “Head-Body-Tail” affords freedom from any particularensemble limitations. For example: a phosphonate head group fornanocrystal binding, alkane body group for length adjustment/nanocrystalspacing and dimethyl silicone tail for silicone matrix compatibility canbe synthesized as shown in FIG. 20 b. An example of tuning the RI(increasing the value) can be realized by incorporation of phenyl groupsshown in FIG. 20 a (similar to silicone polymers (from vendor GelestInc., 612 William Leigh Drive Tullytown, Pa. 19007-6308): DMS-H21dimethylsiloxane vs. HPM-502 phenyl-methylsiloxane, 1.403 and 1.500refractive index values, respectively) in the siloxane tail. FIG. 20 aillustrates several non-limiting example ligands with head-body-taildesign. Matrix compatibility adjustments such as branching siloxaneunits can also be accommodated (FIG. 20 b, molecule 3). Structureverification by NMR of synthesized precursors 1 and 2 in FIG. 20 b isshown in FIGS. 20 c-f.

FIG. 20 g shows additional examples of ligands and synthesis schemes inaccordance with the present invention, including (from top to bottom)the use of trisiloxane, cyclic tetrasiloxane and branched siloxane tailgroups in the generation of ligands. Carboxylic acid functionalizationof these silicone surfactants is illustrated in FIG. 20 g. Structureverification by NMR of a carboxylated trisiloxane ligand shown in FIG.20 g (ligand at top of page) is represented in FIGS. 20 h-i.

It is worth noting that although the ligands can be described in termsof three parts, head, body, and tail, they need not be synthesized fromthese three units. As noted above, three separate groups can besynthesized separately and then combined to produce the ligand. Othersynthesis routes are, however, contemplated; for example, the head andbody can be introduced into the synthesis procedure on a singlemolecule, as illustrated in the syntheses shown in FIGS. 20 g, 20 n, 25a-b, and 27.

FIGS. 20 j and 20 n show further examples and synthesis schemes for theproduction of phosphonate functionalized silicone ligands. Structureverification by NMR of the bromide precursor shown in FIG. 20 j isrepresented in FIG. 20 k. FIGS. 20 l and 20 m represent NMR verificationof the structure of the phosphonate ligand product.

Further examples of suitable ligands are presented below, for example inTable 1, and additional synthesis schemes are shown in FIGS. 25-31 andExamples 3-6 below.

Ligand exchange to displace the surfactants, which are used duringsynthesis, can be done by mass action exchange in solution. Thenanocrystals and the new ligand (e.g., one of those described herein)are co-dissolved in solvent and allowed to react for a specified time atelevated temperatures. The product is precipitated with alcohol toremove any excess unbound ligands and to remove the displaced synthesissurfactants. The attachment is confirmed by NMR analysis by redissolvingthe product into a deuterated NMR compatible solvent. Complexation ofthe ligand with the nanocrystal causes a shift and broadening in thespectrum compared to the free unbound molecule due to a hinderedrotation. As another example, nanostructures are optionally synthesizedusing one (or more) of the novel ligands described herein as thesynthesis surfactant(s).

Nanostructure/Ligand Compositions

One aspect of the invention provides nanostructures having ligands ofthe invention bound to them (e.g., attached, conjugated, coordinated,associated, or otherwise bound to their surface). As describedthroughout, the nanostructures are optionally nanocrystals or quantumdots, e.g., inorganic, semiconductor, or metal nanocrystals. In certainembodiments, the nanostructures are core-shell nanostructures.

One general class of embodiments provides a composition comprising ananostructure and a ligand bound to a surface of the nanostructure,which ligand comprises a body group comprising an organic moiety, a headgroup coupled to the body group, and a tail group coupled to the bodygroup. The head group comprises a nanostructure binding moiety, and thetail group comprises a silicone moiety.

The body group optionally comprises an unsaturated moiety, an arylmoiety, an alkene moiety, an alkyne moiety, or the like. The body groupis optionally a non-conjugated unsaturated moiety.

In other embodiments, the body group comprises an alkyl moiety. Forexample, the body group can be an alkane chain moiety that contains oneor more carbons, e.g., 1-20 carbons. Examples include, but are notlimited to, compounds 11-26 in Table 1. In one embodiment, the bodygroup is a linear alkyl moiety three carbons or four carbons in length.

The nanostructure binding moiety can be essentially any moiety thatbinds or is capable of binding to the surface of the nanostructure. Thebinding can be, for example, covalent, non-covalent, electrostatic,dative, and/or the like. In one class of embodiments, the nanostructurebinding moiety is a carboxylic acid moiety, a monocarboxylic acidmoiety, a dicarboxylic acid moiety, a phosphonate moiety, adiethylphosphonate moiety, a bistrimethylsilylphosphonate moiety, athiol moiety, or an amine moiety. In some embodiments, the head group ismonodentate; in other embodiments, the head group is multidentate, whichcan result in higher affinity binding of the ligand to the nanostructuresurface.

In one class of embodiments, the tail group comprises a linear siliconemoiety. Exemplary ligands include, but are not limited to, compounds11-13 and 16-25 in Table 1. In certain embodiments, the tail includes7-12 dimethylsiloxane units; such compounds are readily soluble insilicone media but are not so large that a highly concentrated solutioncan not be prepared. In other embodiments, the tail group comprises acyclic silicone moiety (e.g., compound 15), a branched silicone moiety(e.g., compound 14), or a silsesquioxane moiety (e.g., a polyhedraloligomeric silsesquioxane (POSS) moiety). Optionally, the siliconemoiety is a moiety other than a silsequioxane moiety or other than aPOSS moiety. The ligand is optionally thermostable, e.g., to 300° C.,400° C., or even 500° C. or more.

One general class of embodiments provides a composition comprising ananostructure and a polymeric ligand bound to a surface of thenanostructure. The polymeric ligand comprises a linear silicone backboneand one or more nanostructure binding moieties coupled to the siliconebackbone.

The polymeric ligand includes two or more monomer units. As just a fewexamples, a monomer unit can be a dimethylsiloxane group, aphenylmethylsiloxane group, or a siloxane group bearing a nanostructurebinding moiety. The monomer units within the ligand can be of the sametype or of different types. In ligands including two or more differenttypes of monomer units, the ligand can, e.g., include a block copolymerof the units (such as in compounds 26-27 and 32-33 in Table 1) or arandom copolymer of the units (such as in compounds 36-39).

As for the embodiments above, the nanostructure binding moiety can beessentially any moiety that binds or is capable of binding to thesurface of the nanostructure, e.g., a carboxylic acid moiety, amonocarboxylic acid moiety, a dicarboxylic acid moiety, a phosphonatemoiety, a diethylphosphonate moiety, a bistrimethylsilylphosphonatemoiety, a thiol moiety, or an amine moiety. The ligand optionallycomprises two or more nanostructure binding moieties, e.g., three ormore, five or more, 10 or more, or even 20 or more.

In one class of embodiments, each of the one or more nanostructurebinding moieties is coupled to the silicone backbone through an alkylmoiety. For example, a nanostructure binding moiety can be coupled tothe silicon atom through a linear alkyl group (examples of such ligandsinclude compounds 26-29 and 32-39 in Table 1). As another example, thenanostructure binding moiety can be coupled to the silicone backbonethrough an alkane chain and a silicone moiety (examples of such ligandsinclude compounds 30-31). In embodiments in which the ligand includestwo or more nanostructure binding moieties, each of the moieties istypically coupled to a different silicon atom in the silicone backbone.

One general class of embodiments provides a composition comprising ananostructure and a ligand bound to a surface of the nanostructure,which ligand comprises a body group comprising an alkyl moiety, a headgroup coupled to the body group, and a tail group coupled to the bodygroup. The head group comprises a nanostructure binding moiety, and thetail group comprises an unsaturated moiety or a silane moiety.

As for the embodiments above, the nanostructure binding moiety can beessentially any moiety that binds or is capable of binding to thesurface of the nanostructure, e.g., a carboxylic acid moiety, amonocarboxylic acid moiety, a dicarboxylic acid moiety, a phosphonatemoiety, a diethylphosphonate moiety, a bistrimethylsilylphosphonatemoiety, a thiol moiety, or an amine moiety.

In one class of embodiments, the body group is a linear alkyl moiety.Examples include, but are not limited to, compounds 40-45 in Table 1.The linear alkyl moiety includes one or more carbons, for example, 1-20carbons. In one embodiment, the body group is a linear alkyl moietythree carbons or four carbons in length.

In embodiments in which the tail group comprises an unsaturated moiety,the moiety can be an alkene moiety (e.g., a monoalkene, dialkene, ordiene), an alkyne moiety, an aromatic moiety, an aryl moiety, or thelike. Exemplary ligands in which the tail group is an alkene moietyinclude compounds 43 and 44 of Table 1. The tail group is optionally anon-conjugated moiety. It is worth noting that certain ligands can bedescribed as alkenes or alkynes bearing one or more nanostructurebinding groups, instead of or in addition to being described in terms ofhead, body, and tail groups.

In embodiments in which the tail group comprises a silane moiety, thesilane moiety includes a silicon atom with three independently selectedorganic substituents. For example, the silicon atom can have threealkene substituents or three aromatic or aryl substituents. In one classof embodiments, the tail group comprises a trialkyl silane moiety.Exemplary ligands in which the tail group comprises a silane moietyinclude compounds 40-42 and 45 of Table 1.

TABLE 1 Exemplary ligands. 11

where m is an integer, e.g., between 1 and 20 (e.g., 3-4), where n is aninteger, e.g., between 0 and 40 (e.g., 2; preferably 7-12), and where Ris the head group 12

where m is an integer, e.g., between 1 and 20 (e.g., 3-4), where n is aninteger, e.g., between 0 and 40 (preferably, 7-12), and where R isselected from the group consisting of

13

where n is an integer, e.g., between 0 and 40 (preferably, 7-12), andwhere R is selected from the group consisting of

14

where R is selected from the group consisting of

15

where R is selected from the group consisting of

16

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, where q is an integer, e.g., between 0 and 40(preferably, 7- 12), and where R′ is Me or Bu 17

where n is an integer, e.g., between 0 and 40 (preferably, 7-12) 18

where n is an integer, e.g., between 0 and 40 (preferably, 7-12, e.g.,8-9) 19

where n and m are integers, and where R is an alkyl group, an arylgroup, or combinations thereof 20

21

22

23

24

25

where n and m are integers, and where R is an alkyl group, an arylgroup, or combinations thereof 26

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, where q is an integer, e.g., between 1 and 40(e.g., 2-40), and where r is an integer, e.g., between 0 and 40 (e.g.,2-40 or 3-40) 27

where n is an integer, e.g., between 1 and 40 (e.g., 2-40), and where mis an integer, e.g., between 0 and 40 (e.g., 2-40 or 3-40) 28

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, and where q is an integer, e.g., between 1 and 4029

where n is an integer, e.g., between 1 and 40 30

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, and where q is an integer, e.g., between 1 and 4031

where n is an integer, e.g., between 1 and 40 32

where R′ is —(OSiMe₂)_(r)SiMe₃, where m is an integer, e.g., between 0and 20, where n is an integer, e.g., between 0 and 20, where o is aninteger, e.g., between 0 and 20, where p is 1, 2, or 3, where q is aninteger, e.g., between 1 and 40, and where r is an integer, e.g.,between 0 and 40 33

where n is an integer, e.g., between 1 and 40, and where m is aninteger, e.g., between 0 and 40 34

where R′ is —(CH₂)_(r)CH₃, where m is an integer, e.g., between 0 and20, where n is an integer, e.g., between 0 and 20, where o is aninteger, e.g., between 0 and 20, where p is 1, 2, or 3, where q is aninteger, e.g., between 1 and 40, and where r is an integer, e.g.,between 0 and 40 35

where n is an integer, e.g., between 1 and 40 36

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, where q is an integer, e.g., between 1 and 40,where r is an integer, e.g., between 0 and 40, and where thedimethylsiloxane moiety and the moiety bearing the dicarboxylic acidnanostructure binding moiety are randomly situated along the siliconebackbone 37

where m is an integer, e.g., between 1 and 40, where n is an integer,e.g., between 0 and 40, and where the dimethylsiloxane moiety and themoiety bearing the dicarboxylic acid nanostructure binding moiety arerandomly situated along the silicone backbone 38

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, where q is an integer, e.g., between 1 and 40,where r is an integer, e.g., between 0 and 40, and where thephenylmethylsiloxane moiety and the moiety bearing the dicarboxylic acidnanostructure binding moiety are randomly situated along the siliconebackbone 39

where m is an integer, e.g., between 0 and 40, where n is an integer,e.g., between 1 and 40, and where the phenylmethylsiloxane moiety andthe moiety bearing the dicarboxylic acid nanostructure binding moietyare randomly situated along the silicone backbone 40

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, where q is an integer, e.g., between 0 and 40,and where r is 1, 2, or 3 41

42

43

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where o is an integer, e.g., between 0 and 20,where p is 1, 2, or 3, and where q is an integer, e.g., between 0 and 4044

45

46

47

where m is an integer, e.g., between 0 and 20, where n is an integer,e.g., between 0 and 20, where p is 1, 2, or 3, and where o is aninteger, e.g., between 0 and 60 (e.g., between 0 and 30) 48

where n is an integer, e.g., between 0 and 60 (e.g., between 0 and 30)

It will be evident that although certain exemplary ligands are shownwith a particular nanostructure binding moiety, the depicted moiety canbe replaced with any other nanostructure binding moiety to obtainanother ligand of the invention (e.g., in compounds 13-48).

As described above, one aspect of the invention provides a wide varietyof novel dicarboxylic and polycarboxylic acid nanostructure ligands.Thus, one general class of embodiments provides a composition includinga nanostructure and a ligand bound to a surface of the nanostructure,where the ligand is a dicarboxylic or polycarboxylic acid other than apoly(norbornene)-poly(norbornene-dicarboxylic acid) diblock copolymer(e.g., any of the carboxylic acid ligands described herein). In oneclass of embodiments, the nanostructure comprises a semiconductor otherthan ZnO or ZnS; for example, the nanostructure can comprise a GroupIII-V semiconductor, a Group IV semiconductor, etc. In another class ofembodiments, the nanostructure is a metal nanostructure, e.g., a Ru, Pd,Pt, Ni, W, Ta, Co, Mo, Ir, Re, Rh, Hf, Nb, Au, Ag, Ti, Sn, Zn, Fe, FePt,or similar nanostructure. In one aspect, the nanostructure is acore-shell nanostructure. Optionally, a plurality of the ligand-boundnanostructures are embedded in a polymer, preferably, a polymercomprising a material different from the carboxylic acid ligand.

Ligands are optionally synthesized, for example, as described herein.Certain ligands are commercially available, e.g., compound 44 (dodecenylsuccinic acid).

A composition of the invention optionally includes a plurality orpopulation of the ligand-bound nanostructures. The nanostructures areoptionally dispersed in a solvent or are optionally embedded in apolymer to form a polymer layer or nanocomposite. Accordingly, in oneaspect, the composition comprises a plurality of the nanostructures,each of which has the ligand bound to its surface, and a polymer inwhich the nanostructures are embedded. The polymer can be, for example,a silicone polymer (e.g., in embodiments in which the ligand has asilicone tail group or substituent) or a hydrocarbon or other organicpolymer (e.g., in embodiments in which the ligand has an alkyl, alkene,or other hydrocarbon tail or substituent). Suitable polymers are wellknown in the art and examples are described herein. Additional exemplaryhydrocarbon polymers include polystyrene, polyethylene, acrylates, andthe like.

In another embodiment, the present invention provides polymeric layers,comprising a polymer and semiconductor nanocrystals embedded within thepolymer, wherein the nanocrystals have miscibility-enhancing ligandsconjugated to their surface, and wherein the ligands comprise an alkanechain of between 6 and 18 carbons in length. In suitable embodiments,the ligands can comprise an alkane chain of between 12 and 18 carbons inlength. The polymer will suitably be silicone, and the semiconductornanocrystals will suitably have a size between about 1-10 nm, and incertain embodiments will be ZnS nanocrystals. In certain embodiments,the polymeric layers will scatter a minimal portion of light that enterssaid polymeric layer. Suitably, the layer will be greater than about 0.5mm in thickness.

V. Processes for Producing Nanocomposites

In another embodiment, as represented in FIG. 21, the present inventionprovides processes for preparing polymeric layers, comprising (a) mixingsemiconductor nanocrystals at a first density with a solvent and apolymer to form a first mixture (2100), (b) coating a substrate materialwith the first mixture (2102), and (c) evaporating the solvent to formthe polymeric layer (2104), wherein the polymeric layer has an effectiverefractive index of n₁.

In suitable embodiments, the processes of the present invention can beused to coat active devices or optical devices. As discussed throughout,nanocrystals useful in the processes of the present invention cancomprise miscibility-enhancing ligands conjugated, coordinated,attached, bound or otherwise associated to their surface. Any of thevarious types of nanocrystals discussed herein can be used in theprocesses of the present invention. For example, high emissionnanocrystals, low emission/high absorption nanocrystals and lowemission/low absorption nanocrystals can be used. In certainembodiments, two or more different types of nanocrystals can be mixedwith the solvent and polymer, thereby creating a composite that hasseveral or all of the properties described herein. Refractive indexmatching applications can utilize any of the nanocrystals discussedthroughout, depending on if the nanocomposite is also required tofunction as a down-converting layer or a filtering layer. In otherapplications, nanocrystals that have low emission/low absorptionproperties are useful in refractive index matching applications whererefractive index effects only are desired.

In other embodiments, as shown in FIG. 21, the processes of the presentinvention can further comprise (d) mixing semiconductor nanocrystals ata second density with a solvent and a polymer to form a second mixture(2106), (e) coating the substrate material with the second mixture(2108), and (f) evaporating the solvent to form a second polymeric layer(2110), wherein the second polymeric layer has an effective refractiveindex of n₂.

In other embodiments, the processes of the present invention can furthercomprise repeating steps (d) through (f) with a third through i^(th)density of semiconductor nanocrystals to produce third through i^(th)polymeric layers, wherein the third through i^(th) polymeric layers haveeffective refractive indices, n₃ through n_(i), respectively (2112). Asused herein, “i” refers to an integer. The present invention encompassesprocesses for producing polymeric layers which comprise any number ofseparate layers used to produce an overall layer, coating, orencapsulant. Each individual layer, 1 through i, can comprise adifferent density of nanocrystals, nanocrystals of a differentcomposition (i.e., high emission or high absorptive properties), andnanocrystals of different sizes. As such, each layer can have adifferent effective refractive index and can have multiple and/ordifferent properties and characteristics.

By providing individual polymeric layers each with a potentiallydifferent effective refractive index, an overall polymeric layer (e.g.,an encapsulating layer) can be generated that has a nanocrystal densitygradient throughout the overall layer, and also an effective refractiveindex gradient throughout the overall layer. FIG. 22 illustrates thatthe effective refractive index of the 1^(st) layer, n₁ (2200), will begreater than any other layer (2202, 2204, 2206), and the effectiverefractive index of the i^(th) layer, n_(i) (2206), will be less thanany other layer (2200, 2202, 2204). It should also be noted that theprocesses of the present invention can be performed in the reverseorder, i.e., where the nanocrystal density and thus the effectiverefractive index of the i^(th) layer is higher than any other layer, andthe effective refractive index of the first layer prepared, n₁, is lessthan any other layer. In other embodiments, the density and effectiverefractive index of the individual layers can be the same, or can beprepared in such a manner that the overall effective refractive index ofthe polymeric layer varies throughout the layer, rather than in a gradedfashion, as in FIG. 22.

As discussed throughout, various known processes can be used to coat asubstrate material with the polymeric layers of the present invention,as would become apparent to people having ordinary skill in the art andbased on the description herein. Suitable coating processes include, butare not limited to, spin coating and screen printing.

In general, spin coating consists of four stages. The first stage is thedeposition of the coating fluid onto the substrate. It can be done usinga nozzle that pours the coating solution out, or can be sprayed onto thesurface, etc. Usually this dispense stage provides a substantial excessof coating solution compared to the amount that will ultimately berequired in the final coating thickness. The second stage is when thesubstrate is accelerated up to its final, desired, rotation speed. Thesecond stage is usually characterized by aggressive fluid expulsion fromthe substrate surface by the rotational motion. Ultimately, thesubstrate reaches its desired speed and the fluid is thin enough thatthe viscous shear drag exactly balances the rotational accelerations.The third stage is when the substrate is spinning at a constant rate andfluid viscous forces dominate fluid thinning behavior. This stage ischaracterized by gradual fluid thinning. Mathematical treatments of theflow behavior show that if the liquid exhibits Newtonian viscosity(i.e., is linear) and if the fluid thickness is initially uniform acrossthe substrate (albeit rather thick), then the fluid thickness profile atany following time will also be uniform, leading to a uniform finalcoating. The fourth stage is when the substrate is spinning at aconstant rate and solvent evaporation dominates the coating thinningbehavior. As the prior stage advances, the fluid thickness reaches apoint where the viscosity effects yield only rather minor net fluidflow. At this point, the evaporation of any volatile solvent specieswill become the dominant process occurring in the coating.

In another embodiment, the processes of the present invention canfurther comprise centrifuging the mixture produced in step 2100 to forma nanocrystal density gradient within the mixture prior to the coatingin 2102. The use of centrifugation creates a gradient within thepolymeric layer as nanocrystals separate in accordance with theirinertia. Various centrifugation speeds or accelerations can be used toproduce the nanocrystal density gradient in the polymeric layers and canreadily be determined by those skilled in the art. The centrifugationspeed selected depends on the size of the nanocrystals and thedifference in density between the nanocrystals and the polymer solutionprior to polymerization, and the centrifugal approach. Centrifugationcan be for a short time at high speed and generate a gradientkinetically where the centrifugation step is timed based on a calculatedor measured centrifugation rate. Alternatively, an equilibrium approachcan be used where the flux of the nanocrystals toward the bottom of acentrifuge tube is matched to the flux of nanocrystals toward the top ofthe tube (due to diffusion). The diffusional flux is proportional to theconcentration gradient of the nanocrystals. Suitably, accelerations canbe in the range of a few hundred times g to 100,000 times g, where g isthe acceleration due to gravity (9.8 m/s²) By selecting nanocrystals ofdifferent sizes and made from different materials, the nanocrystals willspread out through the polymeric layer according to their inertia inresponse to the centrifugation and generate a gradient in the layer. Anyother process known to those skilled in the art to generate gradientswithin polymers may also be used to create the polymeric layers of thepresent invention.

In optical lenses, the optical path length varies with distance from itscenter, where optical path length is defined as the product of thephysical path length, thickness, and the refractive index, n, of thelens material. In the most common lenses, the refractive index, n, isfixed and the thickness, varies. However, a lens can also be created bykeeping the thickness, constant and varying the refractive index as afunction of distance from the axis of the lens. Such a lens is called aGraded Index lens, or sometimes abbreviated as a GRIN lens. The methodsof the present invention can also be used to create GRIN lenses.Polymer/nanocrystal blends can be used to make GRIN lenses due to thedramatic refractive index difference between nanocrystals (e.g., ZnSabout 2.35) and optical plastics such as poly(methyl methacrylate)(PMMA) (refractive index about 1.45). With normal glass, a difference ofabout 0.05 refractive index units is achievable over about 8 mm.Utilizing the methods and processes of the present application, adifference of about 0.20 refractive index units over about 8 mm can beachieved to make much more powerful lenses.

In such embodiments, a gradient pump can be used to inject a solutioncontaining polymer monomers and nanocrystals into the center of a mold,and then nanocrystal concentration can be varied during the fill. Thelens can then be cured and removed.

The polymeric nanocomposites of the present invention can be used in anyapplication where the down-conversion, filtering, and/or refractiveindex characteristics of the composites are desired. Non-limitingexamples of applications of polymeric nanocomposites with increasedrefractive indexes include:

Super High Gloss Coatings: Increasing the refractive index of atransparent coating increases gloss. The addition of nanocrystals (e.g.,ZnS nanocrystals) to polymeric coatings such as waxes and other coatings(e.g., car waxes, shoe waxes, floor coatings and related products) wouldincrease the amount of light that is reflected from the coated surfaceand thus increase the glossiness of its appearance. Appropriate ligands,including C18, PEG and others discussed throughout could be used so asto allow the nanocrystals to be formulated with various polymers, waxesand coatings.

Plastic Eye Glass Lenses and Contacts: The thickness of a lens isproportional to the refractive index of the material of which it made.The higher the refractive index, the thinner the lens. Normal glass hasa refractive index of about 1.523 while an example plastic, such asCR39, has refractive index of 1.49. A plastic lens, although lighter inweight, is thicker than a glass lens of equivalent power.

By incorporating nanocrystals, for example ZnS nanocrystals suitablywith the appropriate ligands, into a plastic lens, the refractive indexcan be increased beyond the level of glass to make ultra-thin lenses. Inapplications such as contact lenses, there is an even more pressing needto create thin lenses due to the importance of oxygen transport throughthe lens to the eye. The refractive index of contact lenses are about1.40. The addition of even a small percentage of nanocrystals (e.g.,about 10% ZnS) would increase the refractive index to about 1.5,therefore allowing for thinner lenses. Ligands such as those discussedthroughout can be used to lock the nanocrystals in place in thepolymeric layer. The addition of nanocrystals with specific absorptiveproperties, e.g., ultraviolet (UV) absorbing nanocrystals, would allowfor the creation of UV (or other wavelength) blocking lenses.

VI. Processes for Producing Nanostructures

Semiconductor nanocrystals, particularly with sizes on the scale of 1-10nm, have emerged as a category of the most promising advanced materialsfor cutting-edge technologies because of their novel properties. Despitethe technological advantages of this new generation of materials,concerns have arisen about potentially harmful interactions ofnanocrystals with biological systems and the environment, for example,potential toxicity. Only a few semiconductor compounds are considered tobe non-toxic, such as zinc sulfide (ZnS), indium phosphide (InP),gallium phosphide (GaP), indium nitride (InN), etc.

For many applications of quantum dots, two factors are typicallyconsidered. The first factor is the ability to absorb and emit visiblelight. This consideration makes InP a highly desirable base material.The second factor is the photoluminescence efficiency (quantum yield).Generally, II-VI quantum dots (such as cadmium selenide) have higherquantum yield than III-V quantum dots (such as InP). The quantum yieldof InP cores produced previously has been very low (<<1%), and thereforethe production of a core-shell structure with InP as the core andanother semiconductor compound with higher bandgap (e.g. ZnS) as theshell has been pursued in attempts to improve the quantum yield.However, previous efforts in this direction have achieved a quantumyield of only 10-20% for two reasons. First, the cores used were of lowquality; therefore, the growth process was accompanied by the appearanceof precipitation. Second, the surfactants used in the syntheses,trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO), are boundweakly with the nanocrystals and therefore provided weak protection tothe nanocrystal surface. Although in one instance the quantum yield ofInP dots was reportedly made as high 20-40% by means of photoetching,those etched dots have poor stability in terms of photoluminescenceefficiency.

See, e.g., Micic et al. (1995) “Synthesis and characterization of InP,GaP, GaInP2 quantum dots” J. Phys. Chem. 99:7754-7759; Guzelian et al.(1996) “Synthesis of size-selected, surface-passivated InP nanocrystals”J. Phys. Chem. 100:7212-7219; Battaglia and Peng (2002) “Formation ofhigh quality InP and InAs nanocrystals in a noncoordinating solvent”Nano Lett. 2:1027-1030; Lucey et al. (2005) “Monodispersed InP QuantumDots Prepared by Colloidal Chemistry in a Noncoordinating Solvent” Chem.Mater. 17:3754-3762; Xu et al. (2006) “Rapid synthesis of high-qualityInP nanocrystals” J. Am. Chem. Soc. 128:1054-1055; Haubold et al. (2001)“Strongly luminescent InP/ZnS core-shell nanoparticles” Chem Phys Chem.2:331; Micic et al. (2000) “Core-shell quantum dots of lattice matchedZnCdSe2 shells on InP cores: experiment and theory” J. Phys. Chem. B104:12149-12156; Bharali et al. (2005) “Folate-Receptor-MediatedDelivery of InP Quantum Dots for Bioimaging Using Confocal andTwo-Photon Microscopy” J. Am. Chem. Soc. 127:11364; Talapin et al.(2002) “Etching of colloidal Inp nanocrystals with fluorides:photochemical nature of the process resulting in high photoluminescenceefficiency” J. Phys. Chem. B 106:12659-12663; Hines and Guyot-Sionnest(1998) “Bright UV-Blue Luminescent Colloidal ZnSe Nanocrystals” J. Phys.Chem. B 102:3655; Li et al. (2004) “High quality ZnSe and ZnSnanocrystals formed by activating zinc carboxylate precursors” NanoLett. 4:2261-2264; Chen et al. (2004) “Colloidal ZnSe, ZnSe/ZnS, andZnSe/ZnSeS quantum dots synthesized from ZnO” J. Phys. Chem. B108:17119-17123; Murray et al. (1993) “Synthesis and characterization ofnearly monodisperse CdE (E=S, Se, Te) semiconductor nanocrystallites”,J. Am. Chem. Soc. 115:8706-8715; Dabbousi et al. (1997) J. Phys. Chem. B101:9463; and Cao and Banin (2000) “Growth and properties ofsemiconductor core/shell nanocrystals with InAs cores” J. Am. Chem. Soc.122:9692-9702.

One aspect of the invention provides methods for synthesizing highquality InP nanostructures, including high quality InP cores which canbe used for production of high quality core-shell nanocrystals. Inpreviously reported work, InP cores were prepared with indium chlorideas the precursor for indium and TOPO (trioctyl phosphine oxide) as thesolvent. The methods of the present invention use novel precursors,surfactants, and/or solvents to synthesize InP cores, for example,indium acetate as the precursor for indium,tris(trimethylsilyl)phosphine as the precursor for phosphorous, and amixture of lauric acid and trioctylphosphine oxide as the growthsolvent, which enables precise control of the resulting InP particlesize and size distribution as well as the surface properties. Inaddition, the resulting cores are extremely stable and have higherquantum yield than has previously been achieved.

Another aspect of the invention provides methods of shell growth, alsofacilitating synthesis of high quality core-shell nanostructures. Forexample, a novel strategy for ZnS shell growth is provided, in whichdiethylzinc and hexamethyldisilthiane are used as precursors and a fattyacid is used as a part of the growth solvent. This enables furthernarrowing of the size distribution and significant increase of quantumyield. In other embodiments, dicarboxylic and polycarboxylic acids,including novel ligands described herein, are used as surfactants. Forexample, shells were grown using a monodicarboxylic acid terminatedpolydimethylsiloxane (DCASi-Me) as the surfactant. With this newsurfactant, the surface of the nanocrystals was better passivated, andthe quantum yield was boosted to greater than 50%.

One general class of embodiments provides methods for production of InPnanostructures. In the methods, a first precursor, e.g., indium acetate,and a second precursor, e.g., tris(trimethylsilyl)phosphine, areprovided. The first and second precursors are reacted in the presence ofan acid and a solvent to produce the nanostructures. The solvent ispreferably a solvent other than octadecene. For example, the solvent canbe TOPO, TOP, benzophenone, hexadecane, octadecane, or another solventwith a similarly high boiling point.

In one class of embodiments, the acid is a fatty acid, for example,lauric acid, capric acid, myristic acid, palmitic acid, or stearic acid.In other embodiments, the acid is a phosphonic acid, a dicarboxylicacid, or a polycarboxylic acid, for example, one of those describedherein or known in the art. Examples include, but are not limited to,phosphonic acids such as hexylphosphonic acid and tetradecylphosphonicacid and carboxylic acids such as heptanedioic acid anddodecenylsuccinoic acid. Dicarboxylic acids are compounds having twocarboxylic acid moieties (e.g., two monocarboxylic acid moieties or onedicarboxylic acid moiety). Polycarboxylic acids are compounds havingthree or more carboxylic acid moieties.

The resulting nanostructures are typically nanocrystals, optionally,small nanocrystals having a narrow distribution of sizes. For example,the average diameter of the resulting nanocrystals can be between 1 and6 nm, e.g., between 1.5 and 5.5 nm, e.g., less than 2.5 nm or less than2.0 nm. In one embodiment, the emission spectrum of the nanocrystals hasan emission maximum of between 500 nm and 750 nm. In one embodiment, aluminescence spectrum of the nanocrystals has a full width at halfmaximum of less than 70 nm (e.g., less than 60 nm, less than 50 nm, oreven 40 nm or less), indicating that the nanocrystals have a narrow sizedistribution.

The methods optionally include using the InP nanostructures as cores andgrowing one or more shells around them, for example, a ZnS, ZnSe,ZnSe_(x)S_(1-x), ZnTe, or ZnO shell. Optionally, the resultingnanostructures have a high quantum efficiency, e.g., greater than 40%,greater than 50%, greater than 55%, or even 60% or higher.

Another general class of embodiments provides methods for production ofcore-shell nanostructures having Group II-VI semiconductor shells. Inthe methods, a nanostructure core is provided, and a shell surroundingthe core is produced by providing a first precursor comprising a GroupII atom, providing a second precursor comprising a Group VI atom, andreacting the first and second precursors in the presence of a ligand toproduce the shell. The precursors are typically reacted in a solvent ormixture of solvents such as TOP, TOPO, etc. Conditions such as thereaction temperature and annealing time can be varied as is known in theart (for either core or shell synthesis).

The ligand is a dicarboxylic or polycarboxylic acid. Exemplary ligandsare described herein, and additional examples can be found in the art.Exemplary ligands include, but are not limited to, compounds 16, 18(DCASi-Me), 43, 44, 46, 47, and 48.

The cores can include essentially any material around which a II-VIshell is desirable. In one class of embodiments, the core comprises aGroup II-VI semiconductor, e.g., CdS, ZnS, ZnSe, or ZnTe. In anotherclass of embodiments, the core comprises a Group III-V semiconductor,e.g., InP, InAs, or In_(1-x)Ga_(x)P.

Similarly, the shell can comprise essentially any desired II-VIsemiconductor. For example, the shell can comprise ZnS, ZnSe, orZnSe_(x)S_(1-x). Exemplary core-shell combinations include, but are notlimited to, InP/ZnS, InP/ZnSe/ZnS core/shell/shell, InP/ZnSe_(x)S_(1-x)core/alloy shell, In_(1-x)Ga_(x)P/ZnS alloy core/shell (optionally forbetter lattice matching between the cores and the shells so as toimprove the quantum yield and making the shell thicker for improvedenvironmental stability), and other non-toxic nanocrystals such asZnSe/ZnS and ZnTe/ZnS core-shell nanocrystals whose emission can coverthe blue to ultra-violet spectral range.

As noted above, the first precursor can be diethylzinc. Other exemplaryfirst precursors include dimethyl zinc, zinc oxide, zinc stearate, andzinc acetate. The second precursor can be, e.g., hexamethyldisilthianeor elemental sulfur.

Compositions produced by or useful in practicing the methods are alsofeatures of the invention. For example, a composition can include afirst precursor, e.g., indium acetate, a second precursor, e.g.,tris(trimethylsilyl)phosphine, an acid, and a solvent. The solvent ispreferably a solvent other than octadecene. For example, the solvent canbe TOPO, TOP, benzophenone, hexadecane, octadecane, or another solventwith a similarly high boiling point. In one class of embodiments, theacid is a fatty acid, for example, lauric acid, capric acid, myristicacid, palmitic acid, or stearic acid. In other embodiments, the acid isa phosphonic acid, a dicarboxylic acid, or a polycarboxylic acid, forexample, one of those described herein or known in the art. Thecomposition optionally includes InP nanostructures, e.g., nanocrystals,optionally, small nanocrystals having a narrow distribution of sizes.Another exemplary composition includes a nanostructure core, a firstprecursor comprising a Group II atom, a second precursor comprising aGroup VI atom, and a dicarboxylic or polycarboxylic acid ligand. Thecomposition optionally includes core-shell nanostructures having GroupII-VI semiconductor shells. Essentially all of the features describedfor the methods above apply to these compositions as well, as relevant.

As noted above, use of the methods and/or ligands of the inventionenable synthesis of nanostructures with high quantum efficiency. Quantumefficiency (also known in the literature as quantum yield) is the numberof defined events which occur per photon absorbed (e.g., the number ofphotons emitted by the nanostructures per photon absorbed by thenanostructures).

Accordingly, one general class of embodiments provides a compositioncomprising a population of nanostructures, which population displays aquantum efficiency of 50% or greater. A member nanostructure of thepopulation (typically, each member of the population) comprises a coreand a shell, which core is other than a Cd-containing core or aPb-containing core. Optionally, the population displays a quantumefficiency of 55% or greater, e.g., about 60% or more.

In one class of embodiments, a ligand is bound to a surface of themember nanostructure (e.g., each member). Exemplary ligands include, butare not limited to, those described herein, for example, dicarboxylicacid ligands such as compounds 16 or 18.

As noted, the core does not contain Cd or Pb. In certain embodiments,the core is a non-heavy-metal containing core, where the heavy metalsare the group of elements between copper and lead on the periodic tableof the elements, having atomic weights between 63.546 and 200.590 andspecific gravities greater than 4.0. In one class of embodiments, thecore comprises a Group II-V semiconductor, e.g., InP. The shell cancomprise essentially any desired material, for example, a Group II-VIsemiconductor such as ZnS, ZnSe, ZnSe_(x)S_(1-x), ZnTe, or ZnO.

In one class of embodiments, the member nanostructure comprises an InPcore. Optionally, the nanostructure comprises a ZnS, ZnSe,ZnSe_(x)S_(1-x), ZnTe, or ZnO shell. A ligand can be bound to a surfaceof the member nanostructure, for example, compound 18.

Essentially all of the features described for the embodiments aboveapply to these embodiments as well, as relevant. For example, thenanostructures can be quantum dots. The nanocrystals can have a narrowsize distribution, the cores can be small (e.g., between 1.5 and 5.5 nmin diameter), and/or the nanocrystals can cover the visible spectralrange, e.g., having an emission wavelength between 500 nm and 750 nm.The nanostructures are optionally dispersed in a solvent, polymer, orthe like. Such highly luminescent nanostructures have a variety ofapplications, e.g., in luminescent nanocomposites, etc.

As noted above, use of the methods and/or ligands of the inventionenable synthesis of small InP nanostructures. Thus, one class ofembodiments provides a composition comprising a population of InPnanocrystals, wherein the average diameter of the nanocrystals in thepopulation is less than 5.5 nm. Preferably, the average diameter of thenanocrystals is less than 2.5 nm, e.g., less than 2.0 nm. In oneembodiment, the average diameter is as small as 1.5 nm or 1 nm. Thenanocrystals optionally have a narrow size distribution.

Also as noted above, use of the methods and/or ligands of the inventionenable synthesis of InP nanostructures having a narrow sizedistribution. Accordingly, one class of embodiments provides acomposition comprising a population of InP nanocrystals, wherein aluminescence spectrum of the population has a full width at half maximumof less than 70 nm. For example, the full width at half maximum can beless than 60 nm, less than 50 nm, or even 40 nm or less. Thenanocrystals are optionally small, e.g., 1-6 nm or 1.5-5.5 nm in size;optionally, the emission spectrum of the population has an emissionmaximum between 500 nm and 750 nm.

VI. Luminescent Nanocomposites

Incorporation of luminescent nanocrystals into a curable matrix isdesirable for fabrication of luminescent, optically transparent solidstate samples of desired shape. However, such incorporation has beendifficult to achieve. In previous attempts at incorporating luminescentnanocrystals into a curable matrix, either the nanocrystals wereincompatible with the matrix, leading to phase separation, or theluminescence was lost after curing, particularly for nanostructures thatdo not contain cadmium.

In one aspect, the present invention provides luminescent nanocompositesand methods for incorporating luminescent nanostructures into curablematrices while preserving the luminescent properties into the solidstate. The nanostructures optionally have ligands bound to theirsurface, including novel ligands of the invention and/or other tightlybinding ligands.

One general class of embodiments thus provides a luminescentnanocomposite comprising a population of luminescent nanocrystals, whichnanocrystals are embedded in a matrix, and which nanocrystalssubstantially retain their luminescence when embedded in the matrix. Thematrix is preferably an epoxy, polyurea, or polyurethane matrix. An“epoxy” is an epoxide polymer that polymerizes and crosslinks when mixedwith a catalyzing agent. “Polyurea” is a polymer created by a chemicalreaction between an isocyanate and an amine. “Polyurethane” is a polymercreated by a chemical reaction between an isocyanate and a polyol. Avariety of suitable matrices are well known in the art.

As noted, the nanocrystals remain luminescent when embedded in thematrix. Thus, light output of the composite is optionally at least 5%,at least 10%, at least 20%, or at least 30% or more of light output of acomparable population of nanocrystals not embedded in the matrix. Forexample, the quantum yield of a luminescent nanocomposite can be 18%,compared to a quantum yield of 53% for corresponding nanocrystals insolution; light output of the composite would thus be 34% that of thefree nanocrystals.

In one class of embodiments, a ligand is bound to a surface of a membernanocrystal (e.g., of each member nanostructure). The ligand can includea nanostructure binding moiety such as an amine moiety or a dicarboxylicacid moiety. Exemplary amine ligands include aliphatic amines, such asdecylamine or octylamine, and polymeric amines. Exemplary dicarboxylicacid ligands include, but are not limited to, those described herein;for example, compounds 43, 44, and 46.

In one aspect, the nanocrystals are non-Cd containing nanocrystals. Inembodiments in which the nanocrystals are core-shell nanocrystals, boththe core and the shell are substantially cadmium free (i.e., aresynthesized from precursors which comprise elements other than cadmium).The non-Cd containing nanocrystals are typically free of cadmium asdetermined by elemental analysis. In one embodiment, the nanocrystalsare core-shell nanocrystals, and the cores comprise a Group III-Vsemiconductor. As just a few examples, the nanocrystals can be InP/ZnS,InP/ZnSe, or InP/ZnSe_(x)S_(1-x), core-shell nanocrystals orInP/ZnSe/ZnS core/shell/shell nanocrystals, e.g., such as thosedescribed above.

A related general class of embodiments provides a luminescentnanocomposite comprising a population of luminescent nanocrystalsembedded in a matrix, wherein a ligand is bound to a surface of a membernanocrystal. The ligand preferably comprises an amine moiety or adicarboxylic acid moiety that binds to the surface of the membernanocrystal. Preferably, as for the embodiments above, the nanocrystalssubstantially retain their luminescence when embedded in the matrix.

The matrix can be essentially any desired matrix, for example, anoptically transparent and/or curable matrix. A variety of matrices arewell known in the art and can be adapted to practice of the presentinvention. In one embodiment, the matrix comprises epoxy, polyurea, orpolyurethane.

Essentially all of the features noted for the embodiments above apply tothese compositions as well, as relevant; for example, with respect totype of nanocrystal, type of ligand, and/or the like. For example, thenanocrystals are optionally non-Cd containing nanocrystals.

A luminescent composite of the invention is optionally formed into adesired three-dimensional shape, used as a coating, etc. Potentialapplications include luminescent solid state nanocrystal-based samplesof any desirable shape, which can be used in toys, design applications,encapsulation applications, etc. It is worth noting that control overnanocrystal size allows for color tuning, which allows for color tuningwhile only one excitation source is needed. Also, the concentration andloading ratios of the nanocrystals in the composite can be varied.

The invention also provides methods of making such luminescentcomposites. Thus, one general class of embodiments provides methods ofproducing a luminescent nanocomposite, in which luminescent nanocrystalsare provided and mixed with one or more matrix precursors to form afirst mixture. The matrix precursors are cured to produce a matrix,e.g., an epoxy, polyurea, or polyurethane matrix, thereby providing thenanocomposite. The resulting nanocomposite comprises the luminescentnanocrystals embedded in the matrix, wherein the nanocrystalssubstantially retain their luminescence when embedded in the matrix. Themethods optionally include casting or forming the first mixture into adesired shape prior to curing the matrix precursors.

Essentially all of the features noted for the embodiments above apply tothese methods as well, as relevant; for example, with respect to lightoutput, composition of the nanocrystals, associated ligands, and/or thelike. For example, providing luminescent nanocrystals optionallycomprises providing luminescent nanocrystals having a ligand bound to asurface of the nanocrystals. The ligand can include an amine moiety or adicarboxylic acid moiety that binds to the surface of the nanocrystals.Exemplary ligands include those noted above, e.g., decylamine,octylamine, and compounds 43, 44, and 46.

A related general class of embodiments also provides methods ofproducing a luminescent nanocomposite. In the methods, luminescentnanocrystals having a ligand bound to a surface of the nanocrystals areprovided. The ligand preferably comprises an amine moiety or adicarboxylic acid moiety that binds to the surface of the nanocrystals.The nanocrystals are mixed with one or more matrix precursors to form afirst mixture, and the matrix precursors are cured to produce a matrix,thereby providing the nanocomposite comprising the luminescentnanocrystals embedded in the matrix. Preferably, the nanocrystalssubstantially retain their luminescence when embedded in the matrix. Themethods optionally include casting or forming the first mixture into adesired shape prior to curing the matrix precursors.

Essentially all of the features noted for the embodiments above apply tothese methods as well, as relevant; for example, with respect tocomposition of the nanocrystals, light output, exemplary ligands, typeof matrix, and/or the like.

EXAMPLES

The following examples are illustrative, but not limiting, of the methodand compositions of the present invention. Other suitable modificationsand adaptations of the variety of conditions and parameters normallyencountered in nanocrystal synthesis, and which would become apparent tothose skilled in the art, are within the spirit and scope of theinvention.

Example 1 Core/shell Nanocrystal Synthesis

Suitable nanocrystal synthesis procedures include fabricatingnanocrystal samples with specific spectral characteristics matched tothose prescribed by the theoretical models of the present invention.This can include fabricating nanocrystals with tunable sizes and sizedistributions (e.g., sizes ranging from 1-20 nm in diameter producingemission peak wavelengths tunable between 460 and 640 nm with FWHMtunable from about 15 to about 100 nm). This in turn is used tosynthesize nanocrystal mixtures identified by simulations that have theoptimal emission characteristics. The simulation and core/shellnanocrystal procedure is typically performed in an iterative process.

Type I core-shell nanocrystals of CdSe/ZnS (core/shell) can besynthesized by a two step process using a solution phase method, firstwith the fabrication of the core material followed by growth of theshell.

Core Synthesis

Stock solutions are prepared of Se powder dissolved intri-n-butylphosphine (TBP), and Cd(CH₃)₂ dissolved in TBP. In anair-free environment, the Cd stock solution is added drop-wise to amixture of trioctylphosphine oxide (TOPO), and trioctylphosphine (TOP),which was previously degassed at 120° C. The temperature is raised to300° C., followed by a quick injection of the Se precursor. Afterinjection, the temperature drops to around 260° C., which is heldconstant for a period of time to control the size of the particle. Bycontrolling the temperature profile and starting reagents andconditions, the center-wavelength and size-distribution can be tunedindependently. The identity of the product is confirmed using XRD andTEM analysis.

Shell Synthesis

Core CdSe nanocrystals are dispersed in TOPO and TOP to which a mixtureof ZnEt₂ and (TMS)₂S will be added at a temperature between 140° C. to220° C. ZnS shell coating thickness will be varied by changing precursorratios and growth temperatures to obtain a uniform surface coverage andto improve the quantum efficiency. The confirmation of shell growth willbe done using XRD, EDX and TEM analysis.

The optical properties of the individual nanocrystals are characterizedby measurement of the UV-Vis absorption and photoluminescence spectrausing a commercial UV-Vis spectrophotometer and a fluorometer. Theexcitation wavelength is matched to the blue LED (about 460 nm).Internal quantum efficiency of the nanocrystals in solution arecalculated using internal reference standards. Nanocrystal componentmixtures (solution phase) are formed by mixing the appropriateconcentration ratios to match the predictions from the theoreticalmodel. The emission and absorption information of these actual mixturesis then back-fed as an input into the simulation to validate (and torefine, if necessary) the model.

The output of this procedure is a solution-phase mixture of nanocrystalsthat has the appropriate composition to produce white light with CRI andCTT matching that of the theoretical model when illuminated with blueexcitation and total down-conversion efficiency comparable to thatpredicted by the model, assuming zero loss to other mechanisms in theprocess.

Example 2 ZnS Nanocrystal Synthesis

In the order listed, add the following to a 50 mL 3-neck round bottomflask:

1. Zn(acetate)₂: 76.5 mg Lot#12727BC

2. Stearic Acid: 484 mg Lot#06615MA

3. Tri-n-octylphosphine oxide (TOPO): 4.07 g Lot#21604LA

In a glove box prepare the following:

3.9 g of distilled tri-n-octylphosphine (TOP) (#35-111) in 5 mL syringe;

116.4 mg of stock solution 02-190 (bis(trimethylsilyl)sulfide(TMS₂S):TOP) in 1 mL syringe; and

One 40 mL septa cap vial with 5.0 mL of MeOH

Place reactor under vacuum

Heat to 120° C.

Once at 120° C., allow to sit for 20 minutes

Place reactor under argon

Slowly inject TOP from 5 mL syringe

Change set point temperature to 250° C.

Once at 250° C., immediately inject the stock solution 02-190(bis(trimethylsilyl)sulfide (TMS₂S):TOP) from 1 mL syringe

Grow with temperature at 250° C. for 2 minutes

Remove the heating mantle and allow reaction to cool to 50° C.

At 50° C., use a syringe to remove the growth solution and inject itinto the 40 mL vial with MeOH.

FIG. 23 shows an X-Ray diffraction scan of ZnS nanocrystals producedaccording the present invention. The scan shows the presence of ZincSulfide with a mixture of wurtzite and zinc blend (spaelite) crystals.

FIG. 24 shows a Transmission Electron Micrograph (TEM) of ZnSnanocrystals (about 4 nm diameter) produced according the presentinvention.

The ZnS nanocrystals can be produced using any chain length hydrocarbon,for example C6-C22 alkane, depending on the application and desiredproperties.

Example 3 Carboxylic Acid-Silicone Ligand Synthesis

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. THF, toluene, chloroform-d₁ and toluene-d₈ weredried over activated 4 A Molecular Sieves and de-gassed by threefreeze-pump-thaw cycles. 4-pentenoic acid and1,1,1,3,5,5,5-heptamethyltrisiloxane were purchased from Aldrich (St.Louis, Mo.), distilled and stored in a storage flask using Schlenktechnique before use. Heptamethyl cyclotetrasiloxane and1,1,1,3,3,5,5-heptamethyl trisiloxane were purchased from Gelest(Morrisville, Pa.), distilled and stored in a storage flask usingSchlenk technique before use. Karstedt's catalyst or platinum divinyltetramethyl disiloxane complex, 2.1 to 2.4% in xylenes, was purchasedfrom Gelest, stored in the glove box and used without furtherpurification. All products were stored in the glove box. NMR chemicalshift data were recorded with a Bruker FT NMR at 400 MHz for ¹H, 100 MHzfor ¹³C{¹H}, 162 MHz for ³¹P{¹H} and 79.5 MHz for ²⁹Si{¹H} and arelisted in ppm.

General Synthesis Procedure (See FIG. 20 g)

Synthesis of HO₂C(CH₂)₄(SiMe₂O)₂SiMe₃

In a glove box, the following reaction was set up in a 100 mL Schlenkflask by addition of Karstedt's catalyst (2.66 g solution, 0.300 mmol)followed by dilution in THF, 60 mL, on the Schlenk line. Then to theclear colorless solution, 1,1,1,3,3,5,5-heptamethyltrisiloxane (8.13 mL,6.67 g, 30.0 mmol) was added by syringe over about 90 seconds and inabout 30 seconds turned the solution clear green. The solution wasstirred at room temperature for about 15 minutes. Then, with thereaction flask surrounded by a room temperature water bath, 4-pentenoicacid (3.07 mL, 3.00 g, 30.0 mmol) was added by syringe over about 90seconds which slowly turned the solution light brown and produced asmall amount of heat. After about 2 hours, the water bath was heated to35° C. using a heater controlled by a thermostat and stirred overnight.

The volatiles were removed from the clear brown solution by rotationalevaporator leaving an opaque brown oil. The product was distilled fromthe mixture by short path apparatus collecting the fraction with vaportemperature between 80 and 95° C. and pressure <20 mtorr. The product isa clear colorless oil (5.55 g or approximately 17 mmol and 57% yield)that typically contains about 50% acid and 50% anhydride. Completeconversion to the acid was accomplished by dissolution of the productmixture (2.00 g or approximately 6.2 mmol) in acetonitrile, 40 mL,followed by addition of pyridine (5.00 mL, 5.11 g, 64.6 mmol) and water(6.20 mL, 6.20 g, 33.4 mmol). The solution was stirred overnight in air.The volatiles were removed from the solution by rotational evaporatoruntil the residue was reduced to an oil. Next, toluene, 100 mL, wasadded and the volatiles removed by rotational evaporator until theresidue was reduced to an oil. The water removal using toluene azeotropewas performed twice. The resulting clear colorless oil was transferredinto a beaker producing a layer about 3 mm thick and the product driedin a desiccator over phosphorous pentoxide under static vacuum of <10mtorr overnight. The product was a clear colorless oil (1.35 g, 4.18mmol, 67% yield) and was stored in the glove box.

Additional carboxylic acid-silicone ligands such as those shown in FIG.20 g and disclosed throughout the present specification, can be preparedusing a procedure similar to that above.

Analysis of HO₂C(CH₂)₄(SiMe₂O)₂SiMe₃

¹H NMR (chloroform-d₁, δ): 0.10, 0.13, 0.14 (s, SiMe), 0.52, 1.39, 1.67(m, CH2), 2.35 (t, 2H, CH2).

¹³C{¹H} NMR (chloroform-d₁, δ): 1.5, 2.0, 2.0 (s, SiMe), 18.1, 23.1,28.5, 34.1 (s, CH2), 180.5 (s, C═O).

²⁹Si{¹H} (1:1 CDCl₃/Et₃N, 0.02 M Cr(acac)₃, δ): −20.9, 7.1 (s, 1:2).

IR (cm⁻¹, diamond): 1050 s (Si—O—Si), 1700 m (C═O), 3030 w (CHaromatic), 2956 sh, 2928 s, 2854 m (CH aliphatic), 3400 to 2700 v br(acid).

Mass Spec ESI (m/z): 345 (MNa⁺).

Data for Synthesis and Analysis of HO₂C(CH₂)₄SiMeO(SiMe₂)₃ (CyclicTetrasiloxane)

The boiling point of the anhydride/acid mixture was 95 to 110° C. at apressure of <10 mbar. The yield for synthesis of the acid/anhydridemixture was about 64% and the conversion to acid was 63%.

¹H NMR (chloroform-d₁, δ): 0.10, 0.12, 0.13 (s, SiMe), 0.48, 1.39, 1.65(m, 2H, CH₂), 2.35 (t, 2H, CH₂).

¹³C{¹H} NMR (chloroform-d₁, δ): −0.1, 1.9, 2.0 (s, SiMe), 17.5, 22.9,28.3, 34.1 (s, CH₂), 180.4 (s, C═O).

²⁹Si{¹H} (1:1 CDCl₃/Et₃N, 0.02 M Cr(acac)₃, δ): −20.3, −19.1, −19.0 (s,1:2:1).

IR (cm⁻¹, diamond): 1050 s (Si—O—Si), 1700 m (C═O), 3030 w (CHaromatic), 2956 sh, 2928 s, 2854 m (CH aliphatic), 3400 to 2700 v br(acid).

Data for Synthesis and Analysis of HO₂C(CH₂)₄SiMe(OSiMe₃)₂

The boiling point of the anhydride/acid mixture was 78 to 95° C. at apressure of <10 mbar. The yield for synthesis of the acid/anhydridemixture was 63% and the conversion to acid was 62%.

¹H NMR chloroform-d₁, δ): 0.10, 0.12, 0.13 (s, SiMe), 0.53, 1.43, 1.68(m, 2H, CH₂), 2.35 (t, 2H, CH₂).

¹³C {¹H} NMR (chloroform-d₁, δ): 0.9, 1.0 (s, SiMe), 16.9, 22.7, 28.1,34.0 (s, CH2), 180.0 (s, C═O).

²⁹Si{¹H} (1:1 CDCl₃/Et₃N, 0.02 M Cr(acac)₃, δ): −22.0, −7.1, (s, 1:2).

IR (cm⁻¹, diamond): 1050 s (Si—O—Si), 1700 m (C═O), 3030 w (CHaromatic), 2956 sh, 2928 s, 2854 m (CH aliphatic), 3400 to 2700 v br(acid).

Mass Spec ESI TOF 381 (MH⁺) and ESI TOF 379 (M-H).

Example 4 Phosphonic Acid Silicone Ligand Synthesis

General Synthesis Procedure

Synthesis of (EtO)₂P(O)(CH₂)₄(SiMe₂O)₂SiMe₃

In a glove box, Karstedt's catalyst (0.450 g solution, 0.052 mmol) wasadded to a 250 mL Schlenk flask. On the Schlenk line, THF, 100 mL, wasadded and followed by 1,1,1,3,5,5,5-heptamethyl trisiloxane (14.0 mL,11.5 g, 51.8 mmol) by syringe over about 90 seconds. The clear colorlesssolution turned clear green in about 30 seconds. The reaction solutionwas stirred for about 15 minutes before addition of diethyl 3-butenylphosphonate (10.0 mL, 9.95 g, 51.8 mmol) by syringe over about 90seconds. The reaction solution then slowly turned light brown andproduced a small amount of heat. After about 2 hours, the reaction flaskwas surrounded by a thermostat controlled water bath that was heated to35° C. The reaction solution was heated overnight.

The volatiles were removed from the clear brown solution by rotationalevaporator leaving an opaque brown oil. A column was packed with silica(230-400 mesh) in hexanes that was 30 mm in diameter and 150 mm long.After placing the crude product on the column, the column was elutedwith hexane, 250 mL, followed by a mixed solvent of 1:1 ratio of ethylacetate to hexane, 1500 mL. The elutant was collected in one fraction.Next the volatiles were then removed by rotational evaporator leaving alight brown oil. The product was then distilled using a simpledistillation at pressure of <20 mtorr and pot temperature of 120° C. Theproduct was a clear colorless oil (17.6 g, 42.5 mmol, 82.1% yield).

Additional phosphonic acid-silicone ligands such as those shown in FIGS.20 a, 20 j and 20 n and disclosed throughout the present specificationcan be prepared using a procedure similar to that above.

Analysis of (EtO)₂P(O)(CH₂)₄(SiMe₂O)₂SiMe₃

¹H NMR (chloroform-d₁, δ): 0.00 (s, 6H, SiMe), 0.05 (s, 6H, SiMe), 0.07(s, 9H, SiMe), 0.53, 1.39, 1.60, 1.70 (m, 2H, CH₂), 1.30 (t, 6H,CH₂CH₃), 4.06 (m, 4H, CH₂CH₃).

¹³C {¹H} NMR (chloroform-d₁, δ): −0.34, 1.46, 2.01 (s, SiMe), 16.68,61.52 (d, JP—C=6 Hz, CH₂CH₃O), 18.05 (s, CH₂), 24.62 (d, JP—C=18 Hz,CH₂), 26.19 (d, JP—C=5 Hz, CH₂), 25.69 (d, JP—C=140 Hz, CH₂P).

³¹P {¹H} NMR (chloroform-d₁, δ): 32.

²⁹Si{¹H} (1:1 CDCl₃, 0.02 M Cr(acac)₃, δ): −22.00, 7.12 (s, 1:2). IR(cm⁻¹, diamond): 1030 (s, Si—O—Si), 1260 (m, Si—Me), 1380, 1400 1430 (w,Et—O—P).

Data for Synthesis and Analysis of (EtO)₂P(O)(CH₂)₄SiMe(OSiMe₃)₂

The pot was heated to 120° C. at a pressure of <20 mtorr to distill theproduct as a clear colorless oil in 81% yield.

¹H NMR (chloroform-d₁, δ): −0.32 (s, 3H, SiMe), 0.06 (s, 18H, SiMe),0.44, 1.37, 1.60, 1.70 (m, 2H, CH₂), 1.30 (t, 6H, CH₂CH₃), 4.08 (m, 4H,CH₂CH₃).

¹³C {¹H} NMR (chloroform-d₁, δ): −0.15, 2.01 (s, SiMe), 16.65, 61.49 (d,JP—C=6 Hz, CH₂CH₃O), 17.38 (s, CH₂), 24.48 (d, JP—C=18 Hz, CH₂), 25.97(d, JP—C=5 Hz, CH₂), 25.71 (d, JP—C=140 Hz, CH₂P).

³¹P {¹H} NMR (chloroform-d₁, δ): 33.

²⁹Si{¹H} (1:1 CDCl₃, 0.02 M Cr(acac)₃, δ): −17.96, 9.94, 10.00 (s,1:1:1).

IR (cm⁻¹, diamond): 1030 (s, Si—O—Si), 1250 (m, Si—Me), 1380, 1400, 1430(w, Et—O—P).

Data for Synthesis and Analysis of (EtO)₂P(O)(CH₂)₄SiMeO(SiMe₂)₃ (cyclictetrasiloxane)

For the distillation the vapor temperature was 84 to 96° C. at apressure of <10 mtorr. The product was isolated as a clear colorless oilin 44% yield.

¹H NMR (chloroform-d₁, δ): 0.50, 0.70 (s, 21H total, SiMe), 0.51 1.41,1.61, 1.69 (m, 2H each, CH₂), 1.30 (t, 6H, CH₂CH₃), 4.08 (m, 4H,CH₂CH₃).

¹³C {¹H} NMR (chloroform-d₁, δ): −0.57, 0.91, 0.94 (s, SiMe), 16.66,61.50 (d, JP—C=6 Hz, CH₂CH₃O), 16.86 (s, CH₂), 24.29 (d, JP—C=18 Hz,CH₂), 25.88 (d, JP—C=5 Hz, CH₂), 25.70 (d, JP—C=140 Hz, CH₂P).

³¹P {¹H} NMR (chloroform-d₁, δ): 33.

²⁹Si{1H} (1:1 CDCl₃, 0.02 M Cr(acac)₃, δ): −20.39, −19.17, −19.08 (s,1:2:1).

IR (cm⁻¹, diamond): 1015, 1050 (s, Si—O—Si), 1250 (m, Si—Me), 1380,1400, 1430 (w, Et—O—P).

General Synthesis Procedure for the Phosphonic Acid,(HO)₂P(O)(CH₂)₄(SiMe₂O)₂SiMe₃

In a 50 mL Schlenk flask, CH₂Cl₂, 15 mL, was added followed by(EtO)₂P(O)(CH₂)₄(SiMe₂O)₂SiMe₃ (1.00 g, 2.42 mmol) and the solutionstirred until homogenous. Then trimethylsilyl bromide (0.671 mL, 0.778g, 5.08 mmol) was added and the solution was stirred for 15 minutes.

The volatiles were removed by vacuum transfer and 10.0 mL of methanolwas added followed by 0.25 mL of water. After stirring for 30 minutes,the volatiles were removed by vacuum transfer and 10.0 mL of toluene wasadded and the solution was stirred for 1 minute. The volatiles wereremoved by vacuum transfer and 10 ml of toluene was added, the solutionstirred and the volatiles removed again, as before. The product was aslightly cloudy viscous oil.

Analysis of (HO)₂P(O)(CH₂)₄(SiMe₂O)₂SiMe₃

ESI (m/z): 359 (MH+) and 381 (MNa+).

Example 5 Synthesis of Aliphatic Carboxylic Acid Ligands

Synthesis of Di-Aliphatic (C18) Mono-Succinic Acid Ligand

Synthesis of the ligand is schematically illustrated in FIG. 25 Panel A.

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. Toluene was dried with an M Braun solventsystem that incorporated molecular sieves and alumina as drying agents.Acetone-d₆ was purified by stirring with anhydrous calcium (II) sulfate(Drierite) for 7 days then distilled ‘trap-to-trap’. Chloroform anddichloromethane were purchased from Fisher Chemical and used asreceived. Octadecyl lithium was purchased from FMC Lithium, stored inthe refrigerator and assayed by titration against biphenylmethanolbefore use. Allyl succinic anhydride was purchased from TCI America,distilled and stored using Schlenk technique until used. Dichloro methylsilane and dimethyl chloro silane were purchased from Acros Organics andtransferred by cannula to a storage flask before use. Karstedt'scatalyst precursor, or platinum divinyl tetramethyl disiloxane complex2.1 to 2.4% in xylenes—low color, was purchased from Gelest, stored inthe glove box and used without further purification. Silica gel 60(230-400 mesh) was purchased from EM Science and used as received.Phosphorous pentoxide was purchased from Fisher Chemical and used asreceived. Activated carbon (coconut shell) and 4 A Molecular Sieves werepurchased from Aldrich and used as received. NMR chemical shift data wasrecorded with a Bruker FT NMR at 400 MHz for ¹H and 100 MHz for ¹³C{¹H}and are listed in ppm. NMR chemical shifts were referenced using protonimpurities in the deuterium solvent. Silicone formula weight wasdetermined by comparison of end-group to repeat unit integration using¹H NMR using a post acquisition delay (d1) of at least 60 seconds foraccuracy. IR analysis was recorded on a Nicolet 6700 FTIR standardizedwith polypropylene.

Synthesis of 251

To a 500 mL Schlenk flask was added toluene (200 mL) and methyl dichlorosilane (3.93 mL, 3.25 g, 28.2 mmoles). The solution was stirred at roomtemperature and octadecyl lithium (160 mL, 56.5 mmoles, 0.353 M intoluene) added by syringe over 10 minutes. During the addition thereaction solution turned from clear colorless to opaque white. About 30minutes after the addition, toluene (100 mL) was added and the reactionsolution was heated with thermostat controlled water bath to 50° C. Itwas held at this temperature for 4 h, then the heat was turned off andthe reaction solution cooled to room temperature overnight. Then thereaction solution was filtered with a filter tip cannula (Fisherbrand P5with particle retention of 5 to 10 μm) and the volatiles removed byrotational evaporator which left an opaque colorless oil. The residuewas dissolved in hexane (250 mL) and filtered again with filter tipcanula. Then the volatiles were removed by vacuum transfer to leave aclear colorless oil, 14.5 g, 26.4 mmoles, 93.5% yield.

It is worth noting that this reaction also works with a less expensiveGrignard reagent. With the Grignard reagent, however, the reactionsolution is heated for 2 days for completion and the product is washedthoroughly to remove the magnesium halide salts.

Analysis of 251

¹H NMR (chloroform-d₁, δ): 0.20, 0.3 (m, SiCH₃, 3H), 0.57 (m,CH₂(CH₂)₁₆CH₃, 4H), 0.88 (t, CH₂(CH₂)₁₆CH₃, 6H), 1.30 (m, CH₂(CH₂)₁₆CH₃,64H), 3.75 (m, Si—H, 1H).

IR (cm⁻¹, diamond): 2108 m (Si—H), 2852 s, 2917 s, 2958 m (sp³ C—H).

Synthesis of 252 and 253 (compound 42)

To a 250 mL Schlenk flask was added toluene (80 mL) and silane 251 (7.00g, 12.7 mmoles) that produced a clear colorless reaction solution withstirring. The reaction solution was heated to 80 C using a thermostatcontrolled oil bath. Then allyl succinic anhydride (1.78 g, 12.7 mmoles)was added followed by Karstedt's catalyst precursor (11.3 mg of 2.2 wt %solution, 0.0013 mmol or 0.0001 eq Pt metal). After about 1 h, a sampleof the reaction solution was prepared for analysis by removal of thevolatiles. IR analysis showed a large Si—H absorbance without ananhydride or vinyl absorbance, indicating that allyl succinic anhydridehad probably been removed during sample preparation via azeotropicdistillation with toluene. Additionally, that the reaction had notinitiated was confirmed by ¹H NMR. Another 0.0001 eq of Karstedt'scatalyst precursor (low color) was added and the progress of thereaction monitored by IR using the Si—H absorbance to indicateconsumption of silane starting material. This cycle was repeated aboutevery 90 minutes, i.e. catalyst addition followed in 90 minutes byanalysis, until the reaction had initiated. Initiation occurred in abouta day and a half when the color of the reaction solution abruptlychanged from clear yellow to clear brown. Sampling followed by IRanalysis indicated that the Si—H absorbance was replaced by two succinicanhydride C═O absorbances (symmetrical and asymmetrical stretches).Following initiation, the reaction solution was heated about 90 minutesto insure complete conversion of starting material. The progress of thereaction was monitored by ¹H NMR analysis using the disappearance of thevinyl resonances and Si—H peak and the appearance of a multiplet for themethylene on the propyl chain bonded to the silicone.

To work up the reaction, the volatiles were removed by rotationalevaporator and the resulting clear brown oil dissolved in chloroform(300 mL). Then 2 g of activated carbon was added and the solutionstirred overnight in air. The solution was filtered through a coarsefilter followed by a filter tip cannula equipped with Fisherbrand P5filter paper (particle retention 5-10 um) and the volatiles removed byrotational evaporator leaving a turbid light yellow-gray oil. Theproduct was then dissolved in chloroform (200 mL) and sent through a0.45 um nylon syringe filter. The complete de-colorization procedure(with activated carbon and syringe filter etc) was performed twice. Thevolatiles were removed to leave clear light brown oily anhydride 252 (˜8g) which was dissolved in chloroform (200 mL) and combined with silicagel 60 (11 g). The volatiles were removed on a roto-evaporator and thedry powder that was isolated was transferred to a chromatography column(55 mm in diameter and 200 mm long). The column was eluted with 500 mLtoluene and then the product 253 was eluted with 500 mL of ethyl acetate(20%)/toluene (80%). Removal of the volatiles gave 1.30 g, 1.80 mmoles,14.4% yield of white waxy dicarboxylic acid 253.

Analysis of 252

¹H NMR (CDCL₃, δ): −0.06 (s, SiCH₃), 0.50, 0.57 (br m, SiCH₂(CH₂)₁₆CH₃)and SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 0.88 (t, CH₂(CH₂)₁₆CH₃), 1.26 (br m,CH₂(CH₂)₁₆CH₃ and SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 1.67 and 1.96 (d-m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 2.70, 3.1 (d-m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 3.3 (m, SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O).

IR (cm⁻¹, diamond): 1781 and 1863 s (C═O).

Analysis of 253

¹H NMR (acetone-d₆, δ): −0.08 (s, SiCH₃, 3H), 0.49 (m, CH₂(CH₂)₁₆CH₃),SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 6H), 0.89 (t, CH₂(CH₂)₁₆CH₃, 6H), 1.26 (m,CH₂(CH₂)₁₆CH₃, 64H), 1.63 (d-m, J_(HH)=68 Hz,SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 4H), 2.43 (d-m, J_(HH)=99 Hz,SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 4H), 2.81 (d-m, J_(HH)=64 Hz,SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 4H), 2.96 (m, SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 1H), 12.21 (m, CO₂H, 2H).

IR (cm⁻¹, diamond): 1703 s (acid C═O), 2852 m, 2917 m, 2954 w, (sp³C—H), 2500 to 3500 broad m (acid OH).

Synthesis of Mono-Aliphatic (C18) Succinic Acid Ligand

Synthesis of the ligand is schematically illustrated in FIG. 25 Panel B.Substitution of dimethyl chloro silane for methyl dichloro silane intothe synthesis above produced the mono aliphatic (C18) monosuccinic acidligand (compound 41), as schematically illustrated in FIG. 25 Panel B.The reactions were performed analogously to the synthesis of otherligands. Analysis of the intermediates and products are below. Synthesisof 254 resulted in 14.7 g, 20.3 mmoles, 91.9% yield; of 255, 12.8 g,28.0 mmoles, 87.7% yield; of 256, 4.00 g, 8.50 mmoles, 30.3% yield.

Analysis of 254

¹H NMR (acetone-d, δ): 0.08 (s, SiCH₃, 3H), 0.62 (m, SiCH₂(CH₂)₁₆CH₃, 2H), 0.89 (t, SiCH₂(CH₂)₁₆CH₃, 3H), 1.30 (s, SiCH₂(CH₂)₁₆CH₃, 32H), 3.89(m, Si—H, 1H).

IR (cm⁻¹, diamond): 2112 m (Si—H), 2852s, 2921 s, 2958 sh (sp³ C—H).

Analysis of 255

¹H NMR (acetone-d₆, δ): −0.01 (m, SiCH3, 6H), 0.55, 0.57 (m,SiCH₂(CH₂)₁₆CH₃ and SiCH₂CH₂CH₂CH(C═O)(CH₂)C═O), 4H), 0.88 (t,CH₂(CH₂)₁₆CH₃), 1.29 (m, SiCH₂(CH₂)₁₆CH₃, 32H), 1.50 (m,SiCH₂CH₂CH₂CH(C═O)(CH₂)C═O), 2H), 1.84 (d-m, J_(HH)=64 Hz,SiCH₂CH₂CH₂CH(C═O)(CH₂)C═O), 2H), 3.03 (d-m, J_(HH)=127 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 2H), 3.34 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 1H).

IR (cm⁻¹, diamond): 1781 s, 1963 m (anhydride C═O symm. and asymm.),2852 s, 2917 s, 2958 sh (sp³ C—H).

Analysis of 256

¹H NMR (acetone-d₆, δ): −0.2 (s, SiCH₃, 6H), 0.54, 0.55 (m,SiCH₂(CH₂)₁₆CH₃, SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 4H), 0.88 (t,SiCH₂(CH₂)₁₆CH₃, 3 H), 1.29 (m, SiCH₂(CH₂)₁₆CH₃, 32H), 1.40 (m,SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 2H), 1.64 (d-m, J_(HH)=40 Hz,SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 2H), 2.55 (d-m, J_(HH)=80 Hz,SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 2H), 2.82 (m, SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H, 1H), 10.69 (m, CO₂H, 2H).

IR (cm⁻¹, diamond): 1691 s (acid C═O), 2852 s, 2917 s, 2954 sh (sp³C—H), 2500 to 3500 (CO₂H).

Synthesis of Aliphatic (C18) Two-Tail Poly-Carboxylic Acid Ligand

Synthesis of the ligand is schematically illustrated in FIG. 26.

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. Toluene was dried in an M Braun solvent systemthat incorporated molecular sieves and alumina as drying agents.Acetone-d₆ was purified by stirring with anhydrous calcium (II) sulfate(Drierite) for 7 days then distilled ‘trap-to-trap’. Chloroform anddichloromethane were purchased from Fisher Chemical and used asreceived. Triethylamine was purchased from Aldrich dry in sure-sealbottles and transferred by cannula (or double tipped needle) intostorage flasks until used. Allyl succinic anhydride was purchased fromTCI America, distilled and stored using Schlenk technique until used.Dichloro methyl silane was purchased from Acros Organics and a new,previously un-opened bottle was used for each synthesis. Monosilanolterminated silicone was special ordered from Gelest. Karstedt's catalystprecursor, or platinum divinyl tetramethyl disiloxane complex 2.1 to2.4% in xylenes—low color, was purchased from Gelest, stored in theglove box and used without further purification. Phosphorous pentoxidewas purchased from Fisher Chemical and used as received. Octadecylmagnesium chloride (in THF), anhydrous diethyl ether, activated carbon(coconut shell) and 4 A Molecular Sieves were purchased from Aldrich andused as received. NMR chemical shift data was recorded with a Bruker FTNMR at 400 MHz for ¹H and 100 MHz for ¹³C{¹H} and are listed in ppm. NMRchemical shifts were referenced using proton impurities in the deuteriumsolvent. Silicone formula weight was determined by comparison ofend-group to repeat unit integration using ¹H NMR using a postacquisition delay (d1) of at least 60 seconds for accuracy. IR analysiswas recorded on a Nicolet 6700 FTIR standardized with polypropylene.

Synthesis of 261

Synthesis of 261 is adapted from U.S. Pat. No. 2,381,366 to Patnode, W.I., 1942, and Manami, H. et al. (1958) Nippon Kagaku Zasski 79:60-65.

A 2000 mL, 3-neck round bottom flask was equipped with an additionfunnel, mechanical stirrer, reflux condenser and nitrogen atmosphere.The nitrogen bubbler consisted of a piece of glass tubing placed into a1 L Erlenmeyer flask containing about 800 mL of water to absorb the HClgas generated in the reaction. To the reaction flask was added diethylether (1 L) and methyl dichloro silane (500 mL, 533 g, 4.80 moles).Water (51.9 mL, 2.88 moles, 0.6 eq) was transferred into the additionfunnel. The reaction was stirred rapidly while water was added overabout 45 minutes and the reaction solution refluxed gently during theaddition. Following the addition the reaction solution was stirred atroom temperature for about 1 h and under positive nitrogen flow thereaction flask was re-fitted for vacuum distillation. The mechanicalstirrer was exchanged for a magnetic stirrer and the reflux condenserwas replaced with an inverted ‘U’ tube connected to a 2 L receiver. Alsothe reaction flask was fitted with a heating mantle with temperaturecontroller that used a thermocouple between reaction flask and heatingmantle. Then the pot was heated to 25° C. and vacuum gradually appliedto the system using a Teflon lined vacuum pump with vacuum controller(Buchi V-800). During evacuation the receiver was cooled in a dryice/ethanol bath while the vacuum was gradually increased to 200 mtorr.Removing the volatiles at this stage required about 4 h and removed ˜75%of the solution volume. Then the receiver was changed to a 1 L Schlenkflask and product was separated from nonvolatile material bydistillation with the same apparatus (an inverted ‘U’ tube connected toa receiver). In this case the receiver was cooled with liquid nitrogenwhile the pressure was gradually dropped to ˜20 mtorr and thetemperature of the pot was gradually increased to 200° C. Thatdistillate was transferred by cannula to a pot connected to a fractioncutter and the product carefully distilled to separate the oligomericproducts. On this reaction scale a fraction cutter with 24/40 standardtaper joints is most convenient. All fractions were clear colorless oilsand were stored in the glove box. Total reaction yield was 57.8% and thefractions are detailed below.

Fraction A, 26.5 g, n=1.38, fwt 258.1, 7.2% yield, collected between 23C at 125 torr to 24 C at 300 mtorr

Fraction B, 22.1 g, n=1.89, fwt 288.8, 6.2% yield, collected between 24C at 300 mtorr and 24 C at 180 mtorr

Fraction C, 27.5 g, n=2.73, fwt 339.9, 8.0% yield, collected between 24C at 180 mtorr and 25 C at 65 mtorr

Fraction D, 23.5 g, n=2.62, fwt 332.7, 6.8% yield, collected between 25C at 65 mtorr and 22 C at 50 mtorr

Fraction E, 37.0 g, n=3.63, fwt 393.4, 11.0% yield, collected between 22C at 50 mtorr and 29 C at 25 mtorr

Fraction F, 16.9 g, n=4.82, fwt 465.0, 5.1% yield, collected between 29C at 25 mtorr and 37 C at 25 mtorr

Fraction G, 22.8 g, n=5.39, fwt 499.3, 7.8% yield, collected between 33C at 25 mtorr and 30 C at 23 mtorr

Fraction H, 17.7 g, n=7.34, fwt 623.8, 5.5% yield, collected between 30C at 23 mtorr and 63 C at 20 mtorr

It is worth noting that the procedure can be optimized and the yield maybe increased somewhat by accurate metering of the water addition rate byusing a syringe pump or similar fluid metering device. Additionally, theyield may be further optimized by increasing the number of equivalentsof water. It is also worth noting that the diethyl ether removed fromthe reaction in the first stage of the work-up will contain un-reactedsilicon chlorides and should be disposed of carefully, since siliconchlorides react exothermically with water.

Analysis of 261 (Fraction A)

¹H NMR (acetone-d₆, δ): 0.26, 0.29, 0.32 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 4.4H), 0.60, 0.65 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 6H), 4.71, 4.74 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 1.4H), 5.23 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 2H).

IR (cm⁻¹, diamond): 497 m (Si—Cl), 1066 m (Si—O—Si), 1266 m (Si—Me),2190 m (Si—H).

Synthesis of 262

To a 500 mL Schlenk flask was added toluene (200 mL) and dichloropolysilane 261 (15.7 g, 54.5 mmoles) that produced a clear colorlessreaction solution with stirring. The reaction solution was immersed in atap water bath at ˜20° C. and octadecyl magnesium chloride (218 mL, 109mmoles, 0.50 M in THF) was added by syringe which turned the reactionsolution opaque white. About 30 minutes after the addition a thermostatcontrolled water bath was set to 50° C. to warm the reaction solutionfor about 6 hrs. The heat was turned off to let the reaction solutioncool to room temperature overnight. The next day the water bath was to50° C. to heat the reaction solution for another 9 hrs. Then aftercooling to room temperature overnight the reaction solution was filteredusing a filter tip canula and Fisherbrand Q8 (particle retention 20 to25 μm). Then the white residue was extracted with hexane (2×150 mL and1×100 mL) and the organic phase combined. The organic phase was washedwith water (8×100 mL) to remove the residual Grignard reaction salts. Inthe first water wash the aqueous phase turned opaque white after mixingbut by the last wash the water was clear without any turbidity aftermixing. The volatiles were removed by vacuum transfer to leave a clearcolorless oil (37.3 g, 49.5 mmoles, 90.9% yield). Proton NMR analysisgave n=1.74 for a formula weight of 743.9 g/mole.

Analysis of 262

¹H NMR (chloroform-d₁, δ): 0.14, 0.15, 0.16, 0.19 (m,[OSi(CH₃)(H)]_(x)CH₂(CH₂)₁₆CH₃, 12H), 0.64 (m,[OSi(CH₃)(H)]_(x)CH₂(CH₂)₁₆CH₃, 4H), 0.88 (t,[OSi(CH₃)(H)]_(x)CH₂(CH₂)₁₆CH₃, 6H), 1.26 (m,[OSi(CH₃)(H)]_(x)CH₂(CH₂)₁₆CH₃, 64 H), 4.64 (m,[OSi(CH₃)(H)]_(x)CH₂(CH₂)₁₆CH₃, 4H). ¹³C{¹H} (chloroform-d₁, δ): −0.9(m, SiCH3), 1.2, 14.4, 17.1, 22.9, 23.1, 29.6, 29.8, 29.9, 30.0, 32.2,33.3 (m, [OSi(CH₃)(H)]_(x)CH₂(CH₂)₁₆CH₃).

IR (cm⁻¹, diamond): 1054 s (Si—O—Si), 1258 m (Si—CH₃), 2128 m (Si—H),2852 s, 2917 s, 2958 m (sp3 C—H).

Synthesis of 263

To a 500 mL Schlenk flask equipped with a reflux condenser was addedpolysilane 262 (15.7 g, 18.8 mmoles) and toluene (150 mL). The reactionsolution was heated to 80° C. using a thermostat controlled oil bath.Then allyl succinic anhydride (10.6 g, 75.7 mmoles, 0.80 eq/eq Si—H) wasadded followed by Karstedt's catalyst precursor (6.71 mg of 2.2 wt %solution, 0.0076 mmol or 0.0001 eq Pt metal). After about 1 h, a sampleof the reaction solution was prepared for analysis by removal of thevolatiles. IR analysis showed a large Si—H absorbance without ananhydride or vinyl absorbance, indicating that allyl succinic anhydridehad probably been removed during sample preparation via azeotropicdistillation with toluene. Additionally, that the reaction had notinitiated was confirmed by ¹H NMR. Another 0.0001 eq of Karstedt'scatalyst precursor (low color) was added and the progress of thereaction monitored by IR using the Si—H absorbance to indicateconsumption of silane starting material. This cycle was repeated aboutevery 90 minutes, i.e. catalyst addition followed in 90 minutes byanalysis, until the reaction had initiated. Initiation occurred in abouta day and a half when the color of the reaction solution abruptlychanged from clear yellow to clear brown. Sampling followed by IRanalysis indicated that the Si—H absorbance was replaced by two succinicanhydride C═O absorbances (symmetrical and asymmetrical stretches).Following initiation, the reaction solution was heated about 90 minutesto insure complete conversion of starting material. The progress of thereaction was monitored by ¹H NMR analysis using the disappearance of thevinyl resonances and Si—H peak and the appearance of a multiplet for themethylene on the propyl chain bonded to the silicone.

To work up the reaction, the volatiles were removed by rotationalevaporator and the resulting clear brown oil dissolved in chloroform(800 mL). Then 4.0 g of activated carbon was added and the solutionstirred overnight in air. The solution was filtered through a coarsefilter followed by a filter tip cannula equipped with Fisherbrand P5filter paper (particle retention 5-10 um) and the volatiles removed byrotational evaporator leaving a turbid light yellow-gray oil. Theproduct was then dissolved in dichloromethane (200 mL) and sent througha 0.45 um nylon syringe filter. The complete de-colorization procedure(with activated carbon and syringe filter etc) was performed twice. Thevolatiles were removed to leave clear very light yellow oil (25.1 g,18.0 mmoles, 95.7% yield).

Analysis of 263

¹H NMR (chloroform-d₁, δ): 0.06, 1.0, 0.12, 0.18 (m, SiCH3, 9H), 0.56,0.57 (m, SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O and/or SiCH₂(CH₂)₁₆CH₃, 10H), 0.89(t, SiCH₂(CH₂)₁₆CH₃, 6H), 1.27 (m, SiCH₂(CH₂)₁₆CH₃, 64H), 1.45 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 1.83 (d-m, J_(HH)=92 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 2.87 (d-m, J_(HH)=176 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 3.16 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 3H). ¹³C{¹H} (chloroform-d₁, δ): partiallisting 170.4, 174.0 (m, C═O anhydride).

IR (cm⁻¹, diamond): 1013 s (Si—O—Si), 1262 m (Si—CH₃), 1789 m, 1867 w,(C═O, sym. and asym.), 2962 m and 2905 w (CH aliphatic).

Synthesis of 264 (See Compound 35)

To a 1000 mL RBF in air was added polyanhydride 263 (25.1 g, 18.0mmoles) and water (340 mL, 18.9 moles). The solution was heated to 120°C. using a heating mantle with temperature control monitored by athermocouple positioned between the flask and heating mantle. Thesolution was stirred rapidly and a temperature of 120° C. was maintainedfor 90 minutes during which time the reaction solution graduallythickened to opaque white mousse. After cooling to room temperature thevolatiles were removed using trap to trap distillation with an inverted‘U’ shaped tube to connect reaction flask and receiver. Duringdistillation the reaction flask was gently heated with a thermostatcontrolled heating mantle (as above) to 30° C. while the receiver wascooled in a dry ice/ethanol bath. The vacuum was maintained at <30mtorr. To remove the last traces of water the product was placed in adesiccator with fresh phosphorous pentoxide and static vacuum of <30mtorr for at least 16 h. This desiccation step was performed twice withfresh phosphorous pentoxide each time. The product was ground into arough white powder before the last overnight in the desiccator. It wastaken into the glove box, weighed and transferred into vials for storage(23.9 g, 16.2 mmoles, 90.1% yield).

Analysis of 264

¹H NMR (acetone-d₆, δ): −0.04 (br m, SiCH3), 0.48 (br m, SiCH₂(CH₂)₁₆CH₃and SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H), 0.88 (t, CH₂(CH₂)₁₆CH₃), 1.29 (m,SiCH₂(CH₂)₁₆CH₃, 32H), 1.70 (m, SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H), 2.45 (brSiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H), 2.9 (br m, SiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H andSiCH₂CH₂CH₂CH(CO₂H)CH₂CO₂H), 11.8 (br s, CO₂H).

IR (cm⁻¹, diamond): 1033 s (Si—O—Si), 1262 m (Si—CH₃), 1732 s (C═O),2848, 2917 s (sp3 C—H), 2500 to 3500 broad m (carboxylic acid OH).

It will be evident that additional ligands can be prepared usingprocedures similar to those above.

Example 6 Synthesis of Polycarboxylic Acid Ligands

Synthesis of Silicone Di-Carboxylic Acid (DCASi-Me)

Synthesis of the ligand is schematically illustrated in FIG. 27.

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. Toluene, chloroform-d₁ and toluene-d₈ weredried over activated 4 A Molecular Sieves and de-gassed by threefreeze-pump-thaw cycles. Acetone-d₆ was purified by stirring withanhydrous CaSO₄ (Drierite) for 7 days then distilled trap-to-trap.Chloroform was purchased from Fisher chemical and used as received.Allylsuccinic anhydride was purchased from TCI America, distilled andstored using Schlenk technique. The monosilane terminated silicone wasspecial ordered from Gelest. Monosilane silicone formula weight wasdetermined by ¹H NMR using a post acquisition delay (d1) of at least 60seconds for accurate integration. Karstedt's catalyst, or platinumdivinyl tetramethyl disiloxane complex 2.1 to 2.4% in xylenes—low color,was purchased from Gelest, stored in the glove box and used withoutfurther purification. Activated carbon was purchased from Aldrich andused without purification. NMR chemical shift data was recorded with aBruker FT NMR at 400 MHz for ¹H and 100 MHz for ¹³C{¹H} and are listedin ppm. NMR chemical shifts were referenced on proton impurities in thedeuterium solvent. IR analysis was recorded on a Nicolet 6700 FTIRstandardized with polypropylene.

Synthesis Procedure for 271 (n=8.8)

To a 1000 mL Schlenk flask with nitrogen atmosphere, reflux condenserand thermostat controlled oil bath was added allylsuccinic anhydride(55.0 g, 0.392 moles), toluene, 200 mL, and monosilane terminatedsilicone (286 g, 0.392 moles, fwt 728.2). The reaction solution wasstirred and when the oil bath temperature reached 80° C. Karstedt'scatalyst precursor was added (355 mg of 2.2 wt % solution, 0.040 mmol or0.0001 eq Pt metal). After about 1 h a sample of the reaction solutionwas prepared for analysis by removal of the volatiles. IR analysisshowed a large Si—H absorbance without an anhydride or vinyl absorbance,indicating that allylsuccinic anhydride had probably been removed duringsample preparation via azeotropic distillation with toluene.Additionally, the analysis indicated the reaction had not initiated,which was confirmed by ¹H NMR. Another 0.001 eq of Karstedt's catalystprecursor was added and the progress of the reaction monitored by IRusing the Si—H absorbance to indicate consumption of silane startingmaterial. This cycle was repeated about every 90 minutes, i.e. catalystaddition followed in 90 minutes by analysis, until the reaction hadinitiated. After about a day and a half, the color of the reactionsolution abruptly changed from clear yellow to clear brown. Then IRanalysis indicated that the Si—H absorbance was replaced by two succinicanhydride C═O absorbances (symmetrical and asymmetrical stretches).About 90 minutes following the color change, complete conversion ofstarting material was confirmed by ¹H NMR analysis using thedisappearance of the vinyl resonances and Si—H peak as well asappearance of a multiplet for the methylene on the propyl chain bondedto the silicone.

To work up the reaction, the volatiles were removed by rotationalevaporator and the resulting clear brown oil decolorized in two parts,each half dissolved in 800 mL chloroform. Then to each solutionactivated carbon, 20 g, was added and the solutions stirred in the airfor 90 minutes. The solutions were filtered through a coarse filterfollowed by a filter tip cannula equipped with Fisherbrand P5 filterpaper (particle retention 5-10 um) and the volatiles removed byrotational evaporator leaving a turbid light yellow-gray oil. Theproduct was then dissolved in 300 mL of chloroform and sent through a0.45 um nylon syringe filter followed by removal of volatiles to leave aclear, very light yellow oil (280 g, 0.323 moles, 82.4% yield).

Analysis of 271 (n=8.8)

¹H NMR (acetone-d₆, δ): 0.13 (m, SiMe, 61.9H), 0.65 (m,O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 2H), 1.56 (m, O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 2H),1.86 (d-m, J=76 Hz, O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 2H), 2.91 (d-q, J_(H-H)=148Hz, J_(H-H)=10 Hz, O₂CCH₂CH(CO)CH₂CH₂CH₂CH₂Si, 2H), 3.32 (m,O₂CCH₂CH(CO)CH₂CH₂CH₂CH₂Si, 1H). ¹³C{¹H} (chloroform-d₁, δ): 1.5 (m,SiMe), 18.5, 21.7, 34.8, 34.9, 41.4 (s, O₂CCH₂CH(CO)CH₂CH₂CH₂Si), 175.6,172.0 (s, O₂CCH₂CH(CO)CH₂CH₂CH₂Si).

IR (cm⁻¹, diamond): 1017 s (Si—O—Si), 1262m (Si—CH₃), 1789 m and 1867 w(C═O, sym. and asym.), 2962 m and 2905 w (CH aliphatic).

Synthesis of 272, HO₂CCH₂CH(CO₂H)(CH₂)₃(SiMe₂O)_(n)SiMe₃ (n=8.8) (seecompound 18)

The reaction solution was divided in half and each part transferred intoa 2000 mL RBF equipped with a reflux condenser in air. To the reactionflask was then added water (730 mL, 40.5 moles or 250 eq) and thesolution heated to 120° C. using a heating mantle with temperaturecontrol monitored by thermocouple positioned between the flask andheating mantle. The solution was rapidly stirred using a mechanicalstirrer as the temperature of 120° C. was maintained for 90 minutes. Asthe reaction proceeded the solution gradually attained the consistencyof mousse and was opaque white. After cooling to room temperature thevolatiles were removed using trap to trap distillation with an inverted‘U’ shaped tube to connect reaction flask and receiver. Duringdistillation the reaction flask was gently heated with a thermostatcontrolled heating mantle (as above) to 30° C. while the receiver wascooled in a dry ice/ethanol bath and the vacuum was maintained at <30mtorr. Then the product was dissolved in chloroform, 100 mL, andfiltered again with 0.45 um syringe filter before final removal ofvolatiles to <30 mtorr for a period of 4 h using dynamic vacuum. Toremove the last traces of water the product was placed in a desiccatorwith fresh P₄O₁₀ and static vacuum of <30 mtorr for at least 16 h. Thisdesiccation step was performed twice with fresh P₄O₁₀ each time. Theclear, very light yellow oil was taken into the glove box, weighed andtransferred into vials for storage (272 g, 0.307 moles, 95.2% yield).

Analysis of HO₂CCH₂CH(CO₂H)(CH₂)₃(SiMe₂O)_(n)SiMe₃ (n=8.8)

¹H NMR (acetone-d₆, δ): 0.11 (m, SiMe, 61.9H), 0.62 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 2H), 1.48 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si,2H), 1.61 (d-m, J_(H-H)=16 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 2H), 2.55(d-q, J_(H-H)=92 Hz, J_(H-H)=10 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 2H),2.83 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 1H), 10.71 (s, HO₂C, 2H). ¹³C{¹H}(chloroform-d₁, δ): 1.8 (m, SiMe), 18.8, 21.6, 36.1, 36.3, 41.5 (s,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si), 173.5, 176.4 (s,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si).

IR (cm⁻¹, diamond): 1017 s (Si—O—Si), 1258 m (Si—CH₃), 1716 m (acidC═O), 2905 m and 2962 w (CH aliphatic), 2500 to 3300 w broad (carboxylicacid).

Synthesis of an Alkene Di-Carboxylic Acid Ligand (DDSA, Compound 44)

Synthesis of the ligand is schematically illustrated in FIG. 28.

General Methods

The starting anhydride (2-dodecen-1-ylsuccinic anhydride) was purchasedfrom Aldrich. Acetone-d₆ was purified by stirring with anhydrous CaSO₄(Drierite) for 7 days then distilled trap-to-trap. NMR chemical shiftdata was recorded with a Bruker FT NMR at 400 MHz for ¹H and 100 MHz for¹³C{¹H} and are listed in ppm. NMR chemical shifts were referenced fromproton impurities in the deuterium solvent. IR analysis was recorded ona Nicolet 6700 FTIR standardized with polypropylene.

Synthesis Procedure

To a 2000 mL round bottom flask equipped with mechanical stirrer andheating mantle (thermocouple between the flask and heating mantle) wasadded anhydride (100 g, 0.375 moles, a waxy white solid) and water (337mL, 18.7 moles) in air. The flask was fitted with a reflux condenser andheated to 120 C using the thermostat to control the temperature with atemperature controller. The reaction solution was stirred rapidly givingit an opalescent appearance initially but as heating was continued itbecame opaque white and thickened a bit. After about 90 minutes at 120 Cthe heat was turned off and the solution cooled to room temperatureovernight. The product was isolated by removing the water by vacuumtransfer. An inverted ‘U’ tube was used to connect the reaction flask toa 1000 mL round bottom flask used as a distillation receiver. Thereceiving flask was cooled with a dry ice/ethanol bath and the vacuumapplied to the system gradually to avoid excessive foaming of thereaction solution. During the distillation the reaction flask was heatedto 30 C using the thermostat controlled heating mantle. The vacuum wasgradually increased until <30 mtorr was reached to remove availablewater. As the water was removed the product turned into a white solidcontaining some powder. Then the product was transferred to acrystallizing dish and the larger chunks broken up to facilitate drying.Then last traces of water were removed at <30 mtorr in a vacuumdesiccator over P₂O₅ overnight under static vacuum. The P₂O₅ wasreplaced and the process repeated again in a desiccator producing aflocculent white powder (97.5 g, 0.343 moles, 91.4% yield).

Analysis

¹H NMR (acetone-d₆, δ): 0.88 (m, CH₃, 3H), 1.28 (m,HO₂CCH₂CH(CO₂H)CH₂CH═CHCH₂(CH₂)₇CH₃, 14H), 2.00 (q,HO₂CCH₂CH(CO₂H)CH₂CH═CHCH₂(CH₂)₇CH₃, 2H), 2.28, 2.37 (d-q,HO₂CCH₂CH(CO₂H)CH₂CH═CHCH₂(CH₂)₇CH₃ 2H), 2.43, 2.63 (d-m,HO₂CCH₂CH(CO₂H)CH₂CH═CHCH₂(CH₂)₇CH₃, 2H), 2.84 (m,HO₂CCH₂CH(CO₂H)CH₂CH═CHCH₂(CH₂)₇CH₃, 1H), 5.40, 5.51 (d-m,HO₂CCH₂CH(CO₂H)CH₂CH═CHCH₂(CH₂)₇CH₃, 2H), 10.75 (s, CO₂H, 2H). ¹³C{¹H}(acetone-d₆, δ): 127, 134 (s, CH═CH), 173, 176 (s, CO₂H), (incompletelisting).

IR (cm⁻¹, diamond): 1691 s (C═O), 2848 m, 2921 m, 2958 w (C—Haliphatic), 3019 w (C═C), 2400-3400 br w (acid OH). It is worth notingthat IR analysis is a reliable tool for distinguishing acid fromanhydride.

Synthesis of a Silicone One-Tail Poly-Carboxylic Acid Ligand

Synthesis of the ligand is schematically illustrated in FIG. 29.

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. Toluene was dried over activated 4 A MolecularSieves and de-gassed by three freeze-pump-thaw cycles. Acetone-d₆ waspurified by stirring with anhydrous calcium (II) sulfate (Drierite) for7 days then distilled ‘trap-to-trap’. Chloroform and dichloromethanewere purchased from Fisher Chemical and used as received.Dimethylformamide (DMF), triethylamine and acetonitrile were purchasedfrom Aldrich dry in sure-seal bottles and transferred by cannula (doubletipped needle) to storage flasks until used. Allyl succinic anhydridewas purchased from TCI America, distilled and stored using Schlenktechnique until used. Methylhydrocyclosiloxanes (D′4) was purchased fromGelest. The material was used as received and was a mixture of ringsizes containing between 3 and 5 SiH(CH3)-O units with the average ringsize being 4. Dimethyl chloro silane was purchased from Aldrich,distilled and stored in a storage flask until used. Monosilanolterminated silicone was special ordered from Gelest. Karstedt's catalystprecursor, or platinum divinyl tetramethyl disiloxane complex 2.1 to2.4% in xylenes—low color, was purchased from Gelest, stored in theglove box and used without further purification. Phosphorous pentoxidewas purchased from Fisher Chemical and used as received. Activatedcarbon (coconut shell) and 4 A Molecular Sieves were purchased fromAldrich and used as received. NMR chemical shift data was recorded witha Bruker FT NMR at 400 MHz for ¹H and 100 MHz for ¹³C{¹H} and are listedin ppm. NMR chemical shifts were referenced using proton impurities inthe deuterium solvent. Silicone formula weight was determined bycomparison of end-group to repeat unit integration using ¹H NMR using apost acquisition delay (d1) of at least 60 seconds for accuracy. IRanalysis was recorded on a Nicolet 6700 FTIR standardized withpolypropylene.

Synthesis of 291

Synthesis of 291 is adapted from Suzuki, Toshio et al. (1989) Polymer30:333-337 and Cella, James A. et al. (1994) J. Organomet. Chem.480:23-26.

To a 250 mL Schlenk flask on the vacuum line was added DMF (0.651 mL,0.017 moles), acetonitrile (15.9 mL, 0.304 moles) and D′4 (40 g, 0.166mol) which formed a colorless cloudy solution initially that becameclear colorless after stirring for about 3 minutes. Then dimethyl chlorosilane (18.0 ml, 15.7 g, 0.166 moles) was added and the reactionsolution did not appear to generate any heat. The reaction solution washeated to 70° C. using a thermostat controlled oil bath for about 16 h(overnight). The product was then isolated from the reaction solution bydistillation. First the solvent was distilled with pot temperature of70° C. which was attained by fitting the flask directly with a shortpath distillation apparatus. The apparatus was not cooled to roomtemperature after heating overnight but the pressure was graduallydecreased with a vacuum regulator (Buchi V-400) and Teflon diaphragmvacuum pump. At about 120 torr the receiver was cooled with an ice bathand when the pressure reached about 40 torr the distillation apparatuswas re-configured. The distillate was discarded and a 14/20 (standardtaper joint) fraction-cutter distillation apparatus was set up andconnected to the vacuum line for a more efficient vacuum. The contentsof the reaction flask were transferred to the fraction cutterdistillation pot by cannula and the temperature of the oil bath (heatingthe pot) was dropped to 35° C. and maintained at 35° C. Vacuum wasapplied to the distillation apparatus and as the pressure reached about40 torr some distillate was collected in the receiver. That distillateevaporated as the pressure was dropped to 500 mtorr. Then below about300 mtorr product was collected in three fractions: fraction A between24° C. at 310 mtorr to 27° C. at 80 mtorr (0.68 g); fraction B at 27° C.at 80 mtorr to 23° C. at 45 mtorr (3.17 g); and then fraction C (1.70g). The apparatus was re-configured to collect fraction C. Distillatewas collected by heating the pot to 100° C., the vacuum at <30 mtorr andthe pot connected directly to the receiver using an inverted ‘U’ tube.By ¹H NMR it was determined that B fraction had 4.9 repeat units(MW=389.5). Based on this molecular weight the yield of fraction B was5.7% (8.14 mmoles). All fractions were clear-colorless oils and werestored in a nitrogen atmosphere.

Analysis of 291

¹H NMR (acetone-d₆, δ): 0.24 (m, ClSiHCH₃(OSiCH₃H)_(n)CH₃, 17.7H), 0.61(s, ClSiHCH₃(OSiCH₃H)_(n)CH₃, 3H), 4.70, 4.75 (m,ClSiHCH₃(OSiCH₃R)_(n)CH₃, 4.7H), 5.24 (m, ClSiHCH₃(OSiCH₃H)_(n)CH₃, 1H).¹³C{¹H} (acetone-d₆, δ): 0.4, 0.7, 1.0, 1.2, 1.3, 3.6 (m, SiMe).

IR (cm⁻¹, diamond): 502 m (Si—Cl), 1046 m (Si—O—Si), 1262 m (Si—Me),2165 m (Si—H).

Synthesis of 292

To a 50 mL Schlenk flask was added toluene (20 mL) and chloropolysilane291 (1.00 g, 2.57 mmoles) that produced a clear colorless reactionsolution with stirring. Then the silanol (2.06 g, 2.57 mmoles) was addedand in less than 15 sec triethylamine (0.430 mL, 0.312 g, 3.08 mmoles)was added. The reaction solution turned opaque white almostinstantaneously and produced a little white vapor but did not appear toproduce any heat. As the reaction solution was stirred for 1 h it becamea bit thicker but continued to stir freely at room temperature. After 1h the volatiles were removed by vacuum transfer. The white residue wasextracted with toluene (3×5 mL) and the filtrate transferred by filtertip cannula (using Fisherbrand P2 filter paper with particle retention1-5 μm) to a separate Schlenk flask. Removal of the volatiles from thefiltrate by vacuum transfer produced as a clear-colorless oil (2.07 g,1.79 mmoles, 60.3% yield). It was taken into the glove box and after acouple of days storage at room temperature turned slightly cloudy. Theoil was filtered again through a 0.45 μm syringe filter before the nextreaction.

Analysis of 292

¹H NMR (acetone-d₆, δ): 0.15 (m, CH₃, 67H), 4.70 (m, SiH, 5.9H). ¹³C{¹H}(acetone-d₆, δ): 0.7, 1.27, 1.46, 2.03 (m, SiMe).

IR (cm⁻¹, diamond): 1021 s (Si—O—Si), 1262 m (Si—CH₃), 2165 m (Si—H).

Synthesis of 293

To a 50 mL Schlenk flask equipped with a reflux condenser was addedpolysilane 292 (2.07 g, 1.79 mmoles), toluene (15 mL) and allyl succinicanhydride (1.19 g, 8.46 mmoles). The reaction solution was stirred andwhen the oil bath temperature reached 80° C. Karstedt's catalystprecursor was added (7.49 mg of 2.2 wt % solution, 0.0008 mmol or 0.0001eq Pt metal). After about 1 h, a sample of the reaction solution wasprepared for analysis by removal of the volatiles. IR analysis showed alarge Si—H absorbance without an anhydride or vinyl absorbance,indicating that allyl succinic anhydride had probably been removedduring sample preparation via azeotropic distillation with toluene.Additionally, that the reaction had not initiated was confirmed by ¹HNMR. Another 0.0001 eq of Karstedt's catalyst precursor (low color) wasadded and the progress of the reaction monitored by IR using the Si—Habsorbance to indicate consumption of silane starting material. Thiscycle was repeated about every 90 minutes, i.e. catalyst additionfollowed in 90 minutes by analysis, until the reaction had initiated.Initiation occurred in about a day and a half when the color of thereaction solution abruptly changed from clear yellow to clear brown.Sampling followed by IR analysis indicated that the Si—H absorbance wasreplaced by two succinic anhydride C═O absorbances (symmetrical andasymmetrical stretches). Following initiation, the reaction solution washeated about 90 minutes to insure complete conversion of startingmaterial. The progress of the reaction was monitored by ¹H NMR analysisusing the disappearance of the vinyl resonances and Si—H peak and theappearance of a multiplet for the methylene on the propyl chain bondedto the silicone.

To work up the reaction the volatiles were removed by rotationalevaporator and the resulting clear brown oil dissolved indichloromethane (100 mL). Then 5 g of activated carbon was added and thesolution stirred overnight in air. The solution was filtered through acoarse filter followed by a filter tip cannula equipped with FisherbrandP5 filter paper (particle retention 5-10 um) and the volatiles removedby rotational evaporator leaving a turbid light yellow-gray oil. Theproduct was then dissolved in chloroform (300 mL) and sent through a0.45 um nylon syringe filter. The complete de-colorization procedure(with activated carbon and syringe filter etc) was performed twice. Thevolatiles were removed to leave clear very light yellow oil (2.19 g,1.21 mmoles, 67.4% yield).

Analysis of 293

¹H NMR (acetone-d, δ): 0.90, 0.12, 0.16 (m, SiCH₃, 149H), 0.69 (m,O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 12H), 1.58 (m, O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 12H),1.88 (d-m, J_(HH)=88 Hz, O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 12H), 3.01 (d-q,J_(H-H)=148 Hz, J_(H-H)=10 Hz, O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 12H), 3.34 (m,O₂CCH₂CH(CO)CH₂CH₂CH₂Si, 6H), 4.78 (m, Si—H, 1H, 80% substitution).¹³C{¹H} (acetone-d₆, δ): 0.2, 0.6, 1.5, 2.0 (m, SiCH₃), 17.8, 18.6,21.6, 34.9, 41.4 (m, O₂CCH₂CH(CO)CH₂CH₂CH₂Si), 172.0, 175.6 (m,anhydride).

IR (cm⁻¹, diamond): 1017 s (Si—O—Si), 1262 m (Si—CH₃), 1785 m, 1867 w,(C═O, sym. and asym.), 2962 m and 2905 w (CH aliphatic).

Synthesis of 294 (See Compound 27)

To a 100 mL RBF in air was added silicone polyanhydride 293 (2.19 g,1.21 moles) and water (25.7 mL, 1.43 moles). The solution was heated to120° C. using a heating mantle with temperature control monitored by athermocouple positioned between the flask and heating mantle. Thesolution was stirred rapidly and a temperature of 120° C. was maintainedfor 90 minutes during which time the reaction solution graduallythickened to opaque white mousse. After cooling to room temperature thevolatiles were removed using trap to trap distillation with an inverted‘U’ shaped tube to connect reaction flask and receiver. Duringdistillation the reaction flask was gently heated with a thermostatcontrolled heating mantle (as above) to 30° C. while the receiver wascooled in a dry ice/ethanol bath. The vacuum was maintained at <30mtorr. To remove the last traces of water the product was placed in adesiccator with fresh phosphorous pentoxide and static vacuum of <30mtorr for at least 16 h. This desiccation step was performed twice withfresh phosphorous pentoxide each time. The clear, very light yellow oilwas taken into the glove box, weighed and transferred into vials forstorage (1.68 g, 0.874 mmoles, 72.2% yield).

Analysis of 294

¹H NMR (acetone-d₆, δ): 0.70, 0.12 (m, SiCH₃, 149H), 0.62 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 12H), 1.50 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si,12H), 1.67 (d-m, J_(HH)=32 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 12H), 2.4(d-m, J_(HH)=88 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 12H), 2.84 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 6H), 10.75 (m, HO₂C, 12H). ¹³C{¹H}(acetone-d₆, δ): 2.0 (m, SiCH₃), 18.3, 18.8, 21.6, 36.2, 36.4, 41.6 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si), 173.7, 176.9 (m, HO₂C).

IR (cm⁻¹, diamond): 1017 s (Si—O—Si), 1262 m (Si—CH₃), 1712 (C═O), 2500to 3500 br (HO₂C).

Synthesis of Silicone Two-Tail Poly-Carboxylic Acid Ligand

Synthesis of the ligand is schematically illustrated in FIG. 30.

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. Toluene was dried in an M Braun solvent systemthat incorporated molecular sieves and alumina as drying agents.Acetone-d₆ was purified by stirring with anhydrous calcium (II) sulfate(Drierite) for 7 days then distilled ‘trap-to-trap’. Chloroform anddichloromethane were purchased from Fisher Chemical and used asreceived. Triethylamine was purchased from Aldrich dry in sure-sealbottles and transferred by cannula (or double tipped needle) intostorage flasks until used. Allyl succinic anhydride was purchased fromTCI America, distilled and stored using Schlenk technique until used.Dichloro methyl silane was purchased from Acros Organics and a new,previously un-opened bottle was used for each synthesis. Monosilanolterminated silicone was special ordered from Gelest. Karstedt's catalystprecursor, or platinum divinyl tetramethyl disiloxane complex 2.1 to2.4% in xylenes—low color, was purchased from Gelest, stored in theglove box and used without further purification. Phosphorous pentoxidewas purchased from Fisher Chemical and used as received. Activatedcarbon (coconut shell) and 4 A Molecular Sieves were purchased fromAldrich and used as received. NMR chemical shift data was recorded witha Bruker FT NMR at 400 MHz for ¹H and 100 MHz for ¹³C{¹H} and are listedin ppm. NMR chemical shifts were referenced using proton impurities inthe deuterium solvent. Silicone formula weight was determined bycomparison of end-group to repeat unit integration using ¹H NMR using apost acquisition delay (d1) of at least 60 seconds for accuracy. IRanalysis was recorded on a Nicolet 6700 FTIR standardized withpolypropylene.

Synthesis of 301

Synthesis of 301 is adapted from U.S. Pat. No. 2,381,366 to Patnode, W.I., 1942, and Manami, H. et al. (1958) Nippon Kagaku Zasski 79:60-65.

A 2000 mL, 3-neck round bottom flask was equipped with an additionfunnel, mechanical stirrer, reflux condenser and nitrogen atmosphere.The nitrogen bubbler consisted of a piece of glass tubing placed into a1 L Erlenmeyer flask containing about 800 mL of water to absorb the HClgas generated in the reaction. To the reaction flask was added diethylether (1 L) and methyl dichloro silane (500 mL, 533 g, 4.80 moles).Water (51.9 mL, 2.88 moles, 0.6 eq) was transferred into the additionfunnel. The reaction was stirred rapidly while water was added overabout 45 minutes and the reaction solution refluxed gently during theaddition. Following the addition the reaction solution was stirred atroom temperature for about 1 h and under positive nitrogen flow thereaction flask was re-fitted for vacuum distillation. The mechanicalstirrer was exchanged for a magnetic stirrer and the reflux condenserwas replaced with an inverted ‘U’ tube connected to a 2 L receiver. Alsothe reaction flask was fitted with a heating mantle with temperaturecontroller that used a thermocouple between reaction flask and heatingmantle. Then the pot was heated to 25 C and vacuum gradually applied tothe system using a Teflon lined vacuum pump with vacuum controller(Buchi V-800). During evacuation the receiver was cooled in a dryice/ethanol bath while the vacuum was gradually increased to 200 mtorr.Removing the volatiles at this stage required about 4 h and removed ˜75%of the solution volume. Then the receiver was changed to a 1 L Schlenkflask and product was separated from nonvolatile material bydistillation with the same apparatus (an inverted ‘U’ tube connected toa receiver). In this case the receiver was cooled with liquid nitrogenwhile the pressure was gradually dropped to ˜20 mtorr and thetemperature of the pot was gradually increased to 200 C. That distillatewas transferred by cannula to a pot connected to a fraction cutter andthe product carefully distilled to separate the oligomeric products. Onthis reaction scale a fraction cutter with 24/40 standard taper jointsis most convenient. All fractions were clear colorless oils and werestored in the glove box. Total reaction yield was 57.8% and thefractions are detailed below.

Fraction A, 26.5 g, n=1.38, fwt 258.1, 7.2% yield, collected between 23C at 125 torr to 24 C at 300 mtorr

Fraction B, 22.1 g, n=1.89, fwt 288.8, 6.2% yield, collected between 24C at 300 mtorr and 24 C at 180 mtorr

Fraction C, 27.5 g, n=2.73, fwt 339.9, 8.0% yield, collected between 24C at 180 mtorr and 25 C at 65 mtorr

Fraction D, 23.5 g, n=2.62, fwt 332.7, 6.8% yield, collected between 25C at 65 mtorr and 22 C at 50 mtorr

Fraction E, 37.0 g, n=3.63, fwt 393.4, 11.0% yield, collected between 22C at 50 mtorr and 29 C at 25 mtorr

Fraction F, 16.9 g, n=4.82, fwt 465.0, 5.1% yield, collected between 29C at 25 mtorr and 37 C at 25 mtorr

Fraction G, 22.8 g, n=5.39, fwt 499.3, 7.8% yield, collected between 33C at 25 mtorr and 30 C at 23 mtorr

Fraction H, 17.7 g, n=7.34, fwt 623.8, 5.5% yield, collected between 30C at 23 mtorr and 63 C at 20 mtorr

It is worth noting that the procedure can be optimized and the yield maybe increased somewhat by accurate metering of the water addition rate byusing a syringe pump or similar fluid metering device. Additionally, theyield may be further optimized by increasing the number of equivalentsof water. It is also worth noting that the diethyl ether removed fromthe reaction in the first stage of the work-up will contain un-reactedsilicon chlorides and should be disposed of carefully, since siliconchlorides react exothermically with water.

Analysis of 301

¹H NMR (acetone-d₆, δ): 0.26, 0.29, 0.32 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 4.4H), 0.60, 0.65 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 6H), 4.71, 4.74 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 1.4H), 5.23 (m,ClSi(CH₃)(H)O[Si(CH₃)(H)O]_(n)Si(CH₃)(H)Cl, 2H).

IR (cm⁻¹, diamond): 497 m (Si—Cl), 1066 m (Si—O—Si), 1266 m (Si—Me),2190 m (Si—H).

Synthesis of 303

To a 250 mL Schlenk flask was added toluene (100 mL) and dichloropolysilane 301 (5.00 g, 10.7 mmoles) that produced a clear colorlessreaction solution with stirring. Then the silanol (13.9 g, 21.5 mmoles)was added and in less than 15 sec triethylamine (3.58 mL, 2.60 g, 25.7mmoles) was added. The reaction solution turned opaque white almostinstantaneously and produced a little white vapor but did not appear toproduce any heat. As the reaction solution was stirred for 5 h it becamea bit thicker but continued to stir freely at room temperature. After 18h the reaction solution was filtered by filter tip canula (usingFisherbrand P5 filter paper with particle retention 5-10 μm) to aseparate Schlenk flask. Then hexane (120 mL) was added and the solutionfiltered again using a filter tip canula with Fisherbrand P5 filterpaper to a separate Schlenk flask. The volatiles were removed by vacuumtransfer to <30 mtorr and the resulting oil filtered with a 0.45 μmsyringe filter to leave clear colorless oil (15.9 g, 9.79 mmoles, 91.5%yield) that was stored in the glove box.

Analysis of 303

¹H NMR (acetone-d₆, δ): 0.08, 0.12, 0.17, 0.22 m,(CH₃)₃SiO[Si(CH₃)₂O]_(m)[Si(H)(CH₃)O]_(n+2)[Si(CH₃)₂O]Si(CH₃)₃, 122H),4.77 (m, (CH₃)₃SiO[Si(CH₃)₂O]_(m)[Si(H)(CH₃)O]_(n+2)[Si(CH₃)₂O]Si(CH₃)₃,6.8H). ¹³C{¹H} (acetone-d₆, δ): 1.2, 1.4, 1.5, 2.1 (m, SiCH₃).

IR (cm⁻¹, diamond): 1017 s (Si—O—Si), 1258 m (Si—CH₃), 2165 m (Si—H),2966, 2909 m (sp3 C—H).

Synthesis of 305

To a 50 mL Schlenk flask equipped with a reflux condenser was addedpolysilane 303 (3.73 g, 2.03 mmoles) and toluene (15 mL). The reactionsolution was heated to 80° C. using a thermostat controlled oil bath.Then allyl succinic anhydride (0.933 g, 6.66 mmoles) was added followedby Karstedt's catalyst precursor (5.09 mg of 2.2 wt % solution, 0.00033mmol or 0.0001 eq Pt metal). After about 1 h, a sample of the reactionsolution was prepared for analysis by removal of the volatiles. IRanalysis showed a large Si—H absorbance without an anhydride or vinylabsorbance, indicating that allyl succinic anhydride had probably beenremoved during sample preparation via azeotropic distillation withtoluene. Additionally, that the reaction had not initiated was confirmedby ¹H NMR. Another 0.0001 eq of Karstedt's catalyst precursor (lowcolor) was added and the progress of the reaction monitored by IR usingthe Si—H absorbance to indicate consumption of silane starting material.This cycle was repeated about every 90 minutes, i.e. catalyst additionfollowed in 90 minutes by analysis, until the reaction had initiated.Vitiation occurred in about a day and a half when the color of thereaction solution abruptly changed from clear yellow to clear brown.Sampling followed by IR analysis indicated that the Si—H absorbance wasreplaced by two succinic anhydride C═O absorbances (symmetrical andasymmetrical stretches). Following initiation, the reaction solution washeated about 90 minutes to insure complete conversion of startingmaterial. The progress of the reaction was monitored by ¹H NMR analysisusing the disappearance of the vinyl resonances and Si—H peak and theappearance of a multiplet for the methylene on the propyl chain bondedto the silicone.

To work up the reaction the volatiles were removed by rotationalevaporator and the resulting clear brown oil dissolved indichloromethane (200 mL). Then 5 g of activated carbon was added and thesolution stirred overnight in air. The solution was filtered through acoarse filter followed by a filter tip cannula equipped with FisherbrandP5 filter paper (particle retention 5-10 um) and the volatiles removedby rotational evaporator leaving a turbid light yellow-gray oil. Theproduct was then dissolved in dichloromethane (200 mL) and sent througha 0.45 um nylon syringe filter. The complete de-colorization procedure(with activated carbon and syringe filter etc) was performed twice. Thevolatiles were removed to leave clear very light yellow oil (3.41 g,1.49 mmoles, 73.3% yield).

Analysis of 305

¹H NMR (acetone-d₆, δ): 0.90, 0.13, 0.15 (m, SiCH3, 122H), 0.68 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 1.60 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 1.87 (d-m, J_(HH)=76 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 3.00 (d-m, J_(HH)=159 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 3.33 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 4H), 4.97 (m, Si—H, 80% substitution).¹³C{¹H} (acetone-d₆, δ): 0.14, 0.8, 1.5, 2.0 (m, SiCH₃), 17.9, 21.5,34.8, 34.9, 41.4 (m, SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 171.9, 175.6 (m, C═Oanhydride).

IR (cm⁻¹, diamond): 1013 s (Si—O—Si), 1262 m (Si—CH₃), 1789 m, 1867 w,(C═O, sym. and asym.), 2962 m and 2905 w (CH aliphatic).

Synthesis of 307 (See Compound 33)

To a 100 mL RBF in air was added silicone polyanhydride 305 (3.41 g,1.49 mmoles) and water (25.7 mL, 1.53 moles). The solution was heated to120° C. using a heating mantle with temperature control monitored by athermocouple positioned between the flask and heating mantle. Thesolution was stirred rapidly and a temperature of 120° C. was maintainedfor 90 minutes during which time the reaction solution graduallythickened to opaque white mousse. After cooling to room temperature thevolatiles were removed using trap to trap distillation with an inverted‘U’ shaped tube to connect reaction flask and receiver. Duringdistillation the reaction flask was gently heated with a thermostatcontrolled heating mantle (as above) to 30° C. while the receiver wascooled in a dry ice/ethanol bath. The vacuum was maintained at <30mtorr. To remove the last traces of water the product was placed in adesiccator with fresh phosphorous pentoxide and static vacuum of <30mtorr for at least 16 h. This desiccation step was performed twice withfresh phosphorous pentoxide each time. The clear, very light yellow oilwas taken into the glove box, weighed and transferred into vials forstorage (3.18 g, 1.34 mmoles, 90.2% yield).

Analysis of 307

¹H NMR (acetone-d₆, δ): 0.80, 0.12 (m, SiCH₃, 122H), 0.63 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 8H), 1.50 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 8H), 1.67 (d-m, J_(HH)=32 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 8H), 2.53 (d-m,J_(HH)=88 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 8H), 2.84 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 6H), 10.73 (m, HO₂C, 12H). ¹³C{¹H}(acetone-d₆, δ): 1.5, 2.0 (m, SiCH₃), 18.2, 21.4, 36.2, 36.3, 41.6 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si), 173.6, 176.7 (m, HO₂C).

IR (cm⁻¹, diamond): 1017 s (Si—O—Si), 1262 m (Si—CH₃), 1716 (C═O), 2500to 3500 br (HO₂C).

Synthesis of Silicone Two-Tail Poly-Carboxylic Acid Ligand with RandomSilicone Backbones

Synthesis of the ligand is schematically illustrated in FIG. 31 Panel A.

General Methods

All manipulations were carried out with strict exclusion of air andmoisture by using Schlenk technique under an atmosphere of dry nitrogen,unless otherwise stated. Toluene was dried in an M Braun solvent systemthat incorporated molecular sieves and alumina as drying agents.Acetone-d₆ was purified by stirring with anhydrous calcium (II) sulfate(Drierite) for 7 days then distilled ‘trap-to-trap’. Chloroform anddichloromethane were purchased from Fisher Chemical and used asreceived. Allyl succinic anhydride was purchased from TCI America,distilled and stored using Schlenk technique until used. Polyhydridesilicones 311, 314 and 317 were purchased from Gelest. Karstedt'scatalyst precursor, or platinum divinyl tetramethyl disiloxane complex2.1 to 2.4% in xylenes—low color, was purchased from Gelest, stored inthe glove box and used without further purification. Phosphorouspentoxide was purchased from Fisher Chemical and used as received.Activated carbon (coconut shell) and 4 A Molecular Sieves were purchasedfrom Aldrich and used as received. NMR chemical shift data was recordedwith a Bruker FT NMR at 400 MHz for ¹H and 100 MHz for ¹³C{¹H} and arelisted in ppm. NMR chemical shifts were referenced using protonimpurities in the deuterium solvent. Silicone formula weight wasdetermined by comparison of end-group to repeat unit integration using¹H NMR using a post acquisition delay (d1) of at least 60 seconds foraccuracy. IR analysis was recorded on a Nicolet 6700 FTIR standardizedwith polypropylene.

Synthesis of 312

To a 50 mL Schlenk flask equipped with a reflux condenser was addedpolysilane 311 (6.69 g, 6.69 mmoles) and toluene (10 mL). The reactionsolution was heated to 80° C. using a thermostat controlled oil bath.Then allyl succinic anhydride (3.00 g, 21.4 mmoles) was added followedby Karstedt's catalyst precursor (19 mg of 2.2 wt % solution, 0.00214mmol or 0.0001 eq Pt metal). After about 1 h, a sample of the reactionsolution was prepared for analysis by removal of the volatiles. IRanalysis showed a large Si—H absorbance without an anhydride or vinylabsorbance, indicating that allyl succinic anhydride had probably beenremoved during sample preparation via azeotropic distillation withtoluene. Additionally, that the reaction had not initiated was confirmedby ¹H NMR. Another 0.0001 eq of Karstedt's catalyst precursor (lowcolor) was added and the progress of the reaction monitored by IR usingthe Si—H absorbance to indicate consumption of silane starting material.This cycle was repeated about every 90 minutes, i.e. catalyst additionfollowed in 90 minutes by analysis, until the reaction had initiated.Initiation occurred in about a day and a half when the color of thereaction solution abruptly changed from clear yellow to clear brown.Sampling followed by IR analysis indicated that the Si—H absorbance wasreplaced by two succinic anhydride C═O absorbances (symmetrical andasymmetrical stretches). Following initiation, the reaction solution washeated about 90 minutes to insure complete conversion of startingmaterial. The progress of the reaction was monitored by ¹H NMR analysisusing the disappearance of the vinyl resonances and Si—H peak and theappearance of a multiplet for the methylene on the propyl chain bondedto the silicone.

To work up the reaction the volatiles were removed by rotationalevaporator and the resulting clear brown oil dissolved indichloromethane (300 mL). Then 5 g of activated carbon was added and thesolution stirred overnight in air. The solution was filtered through acoarse filter followed by a filter tip cannula equipped with FisherbrandP5 filter paper (particle retention 5-10 um) and the volatiles removedby rotational evaporator leaving a turbid light yellow-gray oil. Theproduct was then dissolved in dichloromethane (200 mL) and sent througha 0.45 um nylon syringe filter. The complete de-colorization procedure(with activated carbon and syringe filter etc) was performed twice. Thevolatiles were removed to leave clear very light yellow oil (8.22 g,5.67 mmoles, 84.7% yield).

Analysis of 312

¹H NMR (acetone-d₆, δ): 0.15 (m, SiCH₃, 78H), 0.66 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 1.79 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 1.89 (d-m, J_(HH)=83 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 3.02 (d-m, J_(HH)=155 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 6H), 3.34 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 3H), 4.75 (m, Si—H, 80% substitution).¹³C{¹H} (acetone-d₆, δ): 1.5, 2.0, (m, SiCH₃), 17.8, 21.6, 34.8, 34.9,41.4 (m, SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 171.9, 175.6 (m, C═O anhydride).

IR (cm⁻¹, diamond): 1013 s (Si—O—Si), 1258 m (Si—CH₃), 1785 m, 1867 w,(C═O, sym. and asym.), 2153 w (Si—H), 2962 m (sp³ C—H).

Synthesis of 313 (See Compound 37)

To a 100 mL RBF in air was added silicone polyanhydride 312 (8.22 g,5.67 mmoles) and water (81.6 mL, 5.34 moles). The solution was heated to120° C. using a heating mantle with temperature control monitored by athermocouple positioned between the flask and heating mantle. Thesolution was stirred rapidly and a temperature of 120° C. was maintainedfor 90 minutes during which time the reaction solution graduallythickened to opaque white mousse. After cooling to room temperature thevolatiles were removed using trap to trap distillation with an inverted‘U’ shaped tube to connect reaction flask and receiver. Duringdistillation the reaction flask was gently heated with a thermostatcontrolled heating mantle (as above) to 30° C. while the receiver wascooled in a dry ice/ethanol bath. The vacuum was maintained at <30mtorr. To remove the last traces of water the product was placed in adesiccator with fresh phosphorous pentoxide and static vacuum of <30mtorr for at least 16 h. This desiccation step was performed twice withfresh phosphorous pentoxide each time. The clear, very light yellow oilwas taken into the glove box, weighed and transferred into vials forstorage (7.95 g, 5.39 mmoles, 95.1% yield).

Analysis of 313

¹H NMR (acetone-d₆, δ): 0.10, 0.13 (m, SiCH₃, 78H), 0.62 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 6H), 1.50 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 6H), 1.68 (d-m, J_(HH)=46 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 6H), 2.58 (d-m,J_(HH)=82 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 6H), 2.83 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 3H), 10.77 (m, HO₂C, 12H). ¹³C{¹H}(acetone-d₆, δ): 1.5, 2.0 (m, SiCH₃), 18.2, 21.4, 36.2, 36.3, 41.6 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si), 173.6, 176.8 (m, HO₂C).

IR (cm⁻¹, diamond): 1009 s (Si—O—Si), 1258 m (Si—CH₃), 1712 (C═O), 2157w, (Si—H), 2500 to 3500 br (HO₂C).

Another random backbone silicone poly-carboxylic acid, with m=4 andn=75, was synthesized using similar techniques.

Other silicone poly-carboxylic acid ligands were synthesizedanalogously, e.g., as schematically illustrated in FIG. 31 Panels B andC. Their analyses are provided below. Synthesis of 318 resulted in 5.37g, 2.82 mmoles, 74.0% yield; of 319, 5.33 g, 2.66 mmoles, 94.4% yield.

Analysis of 315

¹H NMR (acetone-d₆, δ): 0.21 (m, SiCH₃, 93H), 0.70 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 40H), 1.60 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 40H), 1.88 (d-m, J_(HH)=70 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 40H), 3.04 (d-m, J_(HH)=163 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 40H), 3.34 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 20H). ¹³C{¹H} (acetone-d₆, δ): 0.3 (m,SiCH₃), 18.1, 21.6, 34.9, 41.4 (m, SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 172.0,175.8 (m, C═O anhydride).

IR (cm⁻¹, diamond): 1009 S, 1054 sh (Si—O—Si), 1258 m (Si—CH₃), 1777 m,1859 w, (C═O, sym. and asym.), 2154 w (Si—H), 2868 w, 2929 m (sp³ C—H).

Analysis of 316 (See Compound 29)

¹H NMR (acetone-d₆, δ): 0.10, 0.16 (m, SiCH₃, 93H), 0.62 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 40H), 1.50 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si,40H), 1.68 (d-m, J_(HH)=25 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 40H), 2.60(d-m, J_(HH)=90 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 40H), 2.85 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 20H), 10.87 (m, HO₂C, 40H). ¹³C{¹H}(acetone-d₆, δ): −0.6, 0.3 (m, SiCH₃), 17.7, 18.3, 21.4, 36.3, 41.7 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si), 174.6, 178.3 (m, HO₂C).

IR (cm⁻¹, diamond): 1008 S, 1082 sh (Si—O—Si), 1254 m (Si—CH₃), 1695(C═O), 2872 w, 2933 w (sp³ C—H), 2500 to 3500 br (HO₂C).

Analysis of 318

¹H NMR (acetone-d₆, δ): 0.13, 0.14, 0.15, 0.23 (m, SiCH₃, 42H), 0.64 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 1.45 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 1.76 (d-m, J_(HH)=73 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 2.91 (d-m, J_(HH)=144 Hz,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 8H), 3.23 (m,SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O, 4H), 7.43, 7.61, 7.67 (m, Ph, 25H).¹³C{¹H} (acetone-d₆, δ): 0.4, 0.5, 0.9, 2.2 (m, SiCH₃), 18.4, 21.7,34.8, 34.9, 41.4 (m, SiCH₂CH₂CH₂C(H)(C═O)(CH₂)C═O), 171.9, 175.6 (m, C═Oanhydride).

IR (cm⁻¹, diamond): 1037 s, 1131 sh (Si—O—Si), 1254 m (Si—CH₃), 1781 m,1867 w, (C═O, sym. and asym.), 2133 w (Si—H), 2864 w, 2958 m (sp³ C—H),3011 w, 3052 w, 3077 w (phenyl).

Analysis of 319 (See Compound 31)

¹H NMR (acetone-d₆, δ): 0.10, 0.16 (m, SiCH₃, 93H), 0.62 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 40H), 1.50 (m, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si,40H), 1.68 (d-m, J_(HH)=25 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 40H), 2.60(d-m, J_(HH)=90 Hz, HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 40H), 2.85 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si, 20H), 10.87 (m, HO₂C, 40H). ¹³C{¹H}(acetone-d₆, δ): −0.6, 0.3 (m, SiCH₃), 17.7, 18.3, 21.4, 36.3, 41.7 (m,HO₂CCH₂CH(CO₂H)CH₂CH₂CH₂Si), 174.6, 178.3 (m, HO₂C).

IR (cm⁻¹, diamond): 1008 s, 1082 sh (Si—O—Si), 1254 m (Si—CH₃), 1695(C═O), 2872 w, 2933 w (sp³ C—H), 2500 to 3500 br (HO₂C).

It will be evident that additional ligands can be prepared usingprocedures similar to those above.

Example 7 Synthesis of Highly Luminescent InP Nanocrystals

A. InP Nanocrystals with Green Emission λ˜530 nm

Chemicals: Indium(III) acetate, Aldrich 99.99%;Tris(trimethylsilyl)phosphine (TMS₃P), Strem 98+%; Lauric acid (LA),Aldrich 99.5+%; Trioctylphosphine oxide (TOPO), Aldrich 99%;Trioctylphosphine (TOP), Aldrich, purified.

For preparing 580 mg (supposing 100% production yield):

A1. Prepare a growth solution (Growth A1) comprised of the followingchemicals in air and place it in a 100 ml 3-neck flask.

Growth A1

2.33 g indium acetate

4 g TOPO

4.8 g LA

A2. Connect the flask with a straight condenser on Schlenk line. Usesepta to stop the two side-necks of the flask.

A3. Evacuate the flask and then purge it with N₂. Repeat this step for 3times.

A4. Heat the solution to 160° C. and keep this temperature for 40 minunder evacuation.

A5. Increase the temperature to 250° C. and keep this temperature for 20min, keep evacuating the system.

A6. Refill the system with N₂ and set temperature to 300° C.

A7. Prepare a stock solution (Stock A1) containing the followingchemicals in the glovebox. Place the mixture in a 20 ml vial and stop itwith a septum.

Stock A1

1 g tris(trimethylsilyl)phosphine

3 g TOP

A8. Nucleation: When the temperature of the growth solution in the flaskreaches 300° C., the room temperature stock solution is loaded into a 10ml glass syringe (with gauge 12, 2 in. needle), and injected into theflask swiftly. Upon injection, temperature should drop to ˜250° C. andthis temperature is maintained for the entire growth process.

A9. Growth: In order to prepare small dots (˜1-2 nm, with greenemission), the reaction is stopped by removing the heater 1 min afterthe injection. Maintaining good stirring is essential for sizedistribution control.

A10. Monitor the reaction using UV-Vis absorption spectroscopy.

A11. After cooling down, transfer the flask into the glovebox under theprotection of N₂. Move the product to a 20 ml vial (with essentialamount of toluene to wash off the crystals in the flask).

A12. Isolation of the nanocrystals: the original solution from thesynthesis is diluted with toluene by a factor of two, and the dots areprecipitated by adding ethanol (volume of ethanol is twice the diluteddot solution). By centrifugation the dots are separated. These separateddots are redissolved in toluene for further treatment (e.g. additionalwashing).

Note A1: Focusing and defocusing of size distribution. Size distribution(SD) is typically one of the most important parameters of concern. Asize focusing technique is employed to obtain dots with narrow SD. Uponinjection, SD is broad but since there are enough free precursors tomaintain a high saturation concentration, SD can be improved bycontinued heating under a lower temperature (which is low enough toprohibit second nucleation). This is because smaller dots grow fasterthan the bigger ones. With the size being focused more and moreprecursors are consumed, the saturation concentration goes down andtherefore SD turns broad again. This is referred to as defocusing. Toban defocusing, additional precursors can be introduced to maintain ahigh saturation concentration.

B. InP Nanocrystals with Red Emission λ˜630 nm

Chemicals: The same chemicals as used in Procedure A.

For preparing 1.8 g dots in terms of InP (supposing 100% productionyield based on the amount of tris(trimethylsilyl)phosphine used; indiumacetate is supplied in excess):

B1. Prepare a growth solution (Growth B1) comprised of the followingchemicals in air and place it in a 100 ml 3-neck flask.

Growth B1

3.496 g indium acetate

5 g TOPO

7.196 g LA

B2. Repeat steps A2-A6.

B3. Prepare a stock solution (Stock B1) containing the followingchemicals in the glovebox. Place the well mixed components in a 20 mlvial and stop it with a septum.

Stock B1

0.8 g tris(trimethylsilyl)phosphine

3 g TOP

B4. Nucleation: When the temperature of Growth B1 in the flask reaches300° C., inject Stock B1 into the flask swiftly. Upon injectiontemperature should drop to ˜250° C. and this temperature is maintainedfor 10 min to allow the crystals grow. Take aliquots to check the peakposition of the absorption spectrum.

B5. Prepare additional growth and stock solutions for further growth.

Stock B2

1.5 g tris(trimethylsilyl)phosphine

6 g TOP.

B6. Add 1 ml Stock B2 dropwise to the growth solution 12 min after theinjection, then add 1 ml additional Stock B2 each time with an intervalof 15 min until it is used up. Monitor the growth through UV-Visabsorption spectroscopy.

B7. After finishing Stock B2, the absorption peak of the crystals was at566 nm, so more indium and phosphorous precursors are needed.

Growth B2

1.119 g indium acetate

2 g TOPO

2.303 g LA

Stock B3

0.8 g tris(trimethylsilyl)phosphine

3 g TOP

B8. Place Growth B2 in a 25 ml 3-neck flask. Repeat steps A2-A6.

B9. Cool the solution (Growth B2) to 70° C. and transfer it into thereaction flask with a 20 ml syringe.

B10. Add Stock B3 in the same manner described in step B6.

B11. Finished adding Stock B3. The absorption peak is at 590 nm. Waitfor 1 h and cool the flask to RT.

B12. Repeat steps A11-A12.

C. InP/ZnS Core-Shell Nanocrystals

Materials and chemicals:

InP dots as synthesized (absorption peak 480-500 nm), isolated from theoriginal reaction solution

Diethylzinc (ZnEt₂), Aldrich 1M solution in hexanes

Hexamethyldisilathiane (TMS₂S, Aldrich purum grade)

TOPO, Aldrich 99%

LA, Aldrich 99.5%

Dicarboxylic acid (DCASi-Me) functionalized silicones (MW˜800), made,e.g., as described above in Example 6

TOP, Aldrich, purified

C1. Prepare the growth (Growth C1) and the stock (Stock C1) solutions.Growth C1 is placed in a 100 ml 3-neck flask and connected to theSchlenk line. The stock is placed in a 25 ml vial and stopped with aseptum.

Growth C1

120 mg InP (dots washed one time with ethanol/toluene) in 5 ml toluene

3 g TOP

3 g TOPO

1 g LA

Stock C1

1.037 g (1.43 ml) ZnEt₂/hexane

3.083 g TMS₂S in TOP (9.09 wt. %)

5.4 g TOP

C2. Pump out toluene in the flask and refill it with N₂, repeat thepumping-refilling for 3 times.

C3. Set temperature to 180° C. Begin adding the stock solution whentemperature reaches 80° C. Add 0.5 ml stock solution within 1 min (Tincreased to 140° C. after the addition).

C4. When T reaches 180° C., add another 0.5 ml Stock C1.

C5. Add 0.5 ml Stock C1 in every 10 min until it is finished.

C6. Wait 10 min and cool the solution down to RT. Transfer it into theglovebox. Move the product in a 20 ml vial.

Note C1: The weight of InP is determined by the optical density of itsdiluted solution in toluene. The amount of ZnEt₂ and TMS₂S calculatedfor growing two monolayer thick (one monolayer of ZnS equals about 0.31nm) ZnS shells on the InP cores (diameter 2 nm).

Note C2: DCASi-Me is used instead of LA for preparing highly luminescentnanocrystals.

Note C3: S/Zn ratio is varied from 1.1 to 0.5. The stock may be dividedinto two parts where Zn and S are in separated stock solutions.

Note C4: to make oxide shell, after step C5, the solution is cooled toand maintained at 100° C. and air is pumped into the solution. Theoxidation process lasts 1-3 h.

Note C5: The shelling is monitored through absorption andphotoluminescence spectra. At the end, the crystals are kept in itsgrowth solution without being diluted, and the solution is kept in airfor storage.

It is worth noting that choice of ligand can affect quantum yield of theresulting nanostructures. For example, a dicarboxylic acid ligand(DCASi-Me) results in nanocrystals with a quantum yield of greater than50%, phosphonic acid, about 40%, and fatty acids, about 30%.

A photoluminescence spectrum of a typical InP/ZnS nanocrystal samplewith green emission is presented in FIG. 32. As noted above, the linewidth (Full Width at Half Maximum, FWHM) of the spectrum is a signatureof the particle size distribution; the smaller the FWHM, the narrowerthe size distribution. The FWHM of the spectrum illustrated in FIG. 32is 40 nm.

FIG. 33 illustrates determination of quantum yield (Φ) of the InP/ZnSnanocrystal sample described in FIG. 32. Panel A presents absorptionspectra of fluorescein dye, with known quantum yield value, used as thereference. Panel B presents photoluminescence spectra of the dye. PanelC presents an absorption spectrum of the nanocrystals, and Panel Dpresents a photoluminescence spectrum of the nanocrystals. Panel E showsthe quantum yield result deduced from the data of Panels A-D. Thequantum yield of the InP/ZnS nanocrystals in this example is 55%.

Example 8 Luminescent Nanocomposites

Luminescent InP/ZnSe/decylamine nanocrystals were incorporated into acurable epoxy while preserving the luminescent properties into the solidstate, as follows. InP/ZnSe core/shell nanocrystals were synthesizedwith decylamine as the surface ligand. The addition of decylaminestrongly increased the luminescence of the InP/ZnSe nanocrystals. Thenanocrystals were washed once using toluene and methanol and resuspendedin 0.5 ml octylamine yielding a concentration of approximately 9 mg/ml.Octylamine was chosen for compatibility with the epoxy matrix and mayprevent the surface ligands of the nanocrystals from coming off thesurface, which may have happened when nanocrystals with other ligandswere previously blended with epoxy. The above described nanocrystalsolution was added to approximately 300-500 mg degassed Part 2 ofLoctite epoxy E-30CL. After that, degassed Part 1 of the same epoxy wasadded in a ratio of approximately 3:1 with respect to Part 2. The samplewas placed on a hot plate at 60° C. for 15 min in order to cure theepoxy matrix precursors. The entire sample preparation was done in inertatmosphere in a glovebox.

As another example, InP/ZnS nanocrystals were synthesized with thedicarboxylic acid DDSA (compound 44) as the surface ligand. The crystalswere added in a similar fashion to Part B of the non-yellowing epoxyEpo-Tek 301-2 from Epoxy Technology at similar concentration asdescribed above. After that, Part A of the same epoxy was added suchthat A:B was 3:1, and the sample was heated in the glovebox at 60° C.for 2 hours. All work was done in the glovebox. The resulting sample wassolid, clear and luminescent of green color (when the crystals werewashed 1×) or green-yellow (unwashed nanocrystals). Green InP/ZnSenanocrystals with a decylamine ligand were similarly successfullyincorporated into an Epo-Tek epoxy matrix.

As another example, InP/ZnS nanocrystals were synthesized with DDSA asthe surface ligand and added into a urethane matrix. The nanocrystalswere added directly from the growth solution into Part A of urethane setWC783 (BJB Enterprises), such that the resulting optical density wasabout 0.1 at the peak of the emission wavelength. (The concentration ofthe nanocrystals can also be varied to achieve stronger luminescence.)After vortexing, aniline was added, replacing Part B of the urethaneset, and the ratio A:aniline was 3.3:1. After vortexing, the mixture wascentrifuged for a few seconds to remove bubbles from the mixture. In afinal step, the mixture was cured at room temperature for less than 5minutes. All work was done in air. The resulting sample was solid,clear, and luminescent of green color. As another example, rednanocrystals were successfully mixed into the urethane matrix. Allresulting samples were clear and luminescent. The samples still showedluminescence after keeping in air in an oven at 60° C. for 3 months.

Optical properties of the nanocrystals can be characterized bymeasurement of the UV-Vis absorption and photoluminescence spectra usinga commercial UV-Vis spectrophotometer and a fluorometer. Internalphotoluminescence quantum efficiency of the nanocrystals in solution arecalculated using reference standards of known quantum yields.Photoluminescence quantum efficiencies of the nanocrystals in a solidmatrix are determined using an integrating sphere. The quantum yield ofan exemplary luminescent nanocomposite is 18%, compared to a quantumyield of 53% for corresponding nanocrystals in solution.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the invention.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

1. A luminescent nanocomposite, comprising: a population of luminescentnanocrystals, which nanocrystals are embedded in an epoxy, polyurea, orpolyurethane matrix, and which nanocrystals substantially retain theirluminescence when embedded in the matrix, wherein a ligand is bound to asurface of a member nanocrystal, which ligand a) comprises adicarboxylic acid moiety that binds to the surface of the membernanocrystal or b) is an aliphatic or polymeric amine comprising an aminemoiety that binds to the surface of the member nanocrystal.
 2. Thenanocomposite of claim 1, wherein light output of the composite is atleast 10% of light output of a comparable population of nanocrystals notembedded in the matrix.
 3. The nanocomposite of claim 1, wherein theligand comprises dicarboxylic acid moiety that binds to the surface ofthe member nanocrystal.
 4. The nanocomposite of claim 1, wherein theligand is decylamine or octylamine.
 5. The nanocomposite of claim 3,wherein the ligand is selected from the group consisting of:

where m is an integer between 0 and 20, where n is an integer between 0and 20, where o is an integer between 0 and 20, where p is 1, 2, or 3,and where q is an integer between 0 and 40;


6. The nanocomposite of claim 1, wherein the nanocrystals are non-Cdcontaining nanocrystals.
 7. The nanocomposite of claim 1, wherein thenanocrystals are core-shell nanocrystals, wherein the cores comprise aGroup III-V semiconductor.
 8. The nanocomposite of claim 1, wherein thenanocrystals comprise InP/ZnS or InP/ZnSe core-shell nanocrystals orInP/ZnSe/ZnS core/shell/shell nanocrystals.
 9. A luminescentnanocomposite, comprising: a population of luminescent nanocrystalsembedded in a matrix, wherein a ligand is bound to a surface of a membernanocrystal, which ligand comprises a dicarboxylic acid moiety thatbinds to the surface of the member nanocrystal.
 10. The nanocomposite ofclaim 9, wherein the nanocrystals substantially retain theirluminescence when embedded in the matrix.
 11. The nanocomposite of claim9, wherein the ligand is selected from the group consisting of:

where m is an integer between 0 and 20, where n is an integer between 0and 20, where o is an integer between 0 and 20, where p is 1, 2, or 3,and where q is an integer between 0 and 40;


12. The nanocomposite of claim 9, wherein the matrix comprises epoxy,polyurea, or polyurethane.
 13. A method of producing a luminescentnanocomposite, the method comprising: providing luminescent nanocrystalshaving a ligand bound to a surface of the nanocrystals, which ligand a)comprises a dicarboxylic acid moiety that binds to the surface of thenanocrystals or b) is an aliphatic or polymeric amine comprising anamine moiety that binds to the surface of the nanocrystals; mixing thenanocrystals with one or more matrix precursors to form a first mixture;and curing the matrix precursors to produce an epoxy, polyurea, orpolyurethane matrix, thereby providing the nanocomposite; whichnanocomposite comprises the luminescent nanocrystals embedded in thematrix, and which nanocrystals substantially retain their luminescencewhen embedded in the matrix.
 14. The method of claim 13, wherein theligand comprises a dicarboxylic acid moiety that binds to the surface ofthe nanocrystals.
 15. The method of claim 13, wherein the ligand isselected from the group consisting of: decylamine; octylamine;

where m is an integer between 0 and 20, where n is an integer between 0and 20, where o is an integer between 0 and 20, where p is 1, 2, or 3,and where q is an integer between 0 and 40;


16. The method of claim 13, the method comprising casting or forming thefirst mixture into a desired shape prior to curing the matrixprecursors.
 17. The method of claim 13, wherein light output of theresulting nanocomposite is at least 10% of light output of a comparablepopulation of nanocrystals not embedded in the matrix.
 18. The method ofclaim 13, wherein the nanocrystals are non-Cd containing nanocrystals.19. A method of producing a luminescent nanocomposite, the methodcomprising: providing luminescent nanocrystals having a ligand bound toa surface of the nanocrystals, which ligand comprises a dicarboxylicacid moiety that binds to the surface of the nanocrystals; mixing thenanocrystals with one or more matrix precursors to form a first mixture;and curing the matrix precursors to produce a matrix, thereby providingthe nanocomposite; which nanocomposite comprises the luminescentnanocrystals embedded in the matrix.
 20. The method of claim 19, whereinthe nanocrystals substantially retain their luminescence when embeddedin the matrix.
 21. The method of claim 19, wherein the ligand isselected from the group consisting of:

where m is an integer between 0 and 20, where n is an integer between 0and 20, where o is an integer between 0 and 20, where p is 1, 2, or 3,and where q is an integer between 0 and 40;


22. The method of claim 19, wherein the matrix comprises epoxy,polyurea, or polyurethane.
 23. The method of claim 19, the methodcomprising casting or forming the first mixture into a desired shapeprior to curing the matrix precursors.